The ANSI escape sequences you're looking for are the Select Graphic Rendition subset. All of these have the form

\033[XXXm

where XXX is a series of semicolon-separated parameters.

To say, make text red, bold, and underlined (we'll discuss many other options below) in C you might write:

printf("\033[31;1;4mHello\033[0m");

In C++ you'd use

std::cout<<"\033[31;1;4mHello\033[0m";

In Python3 you'd use

print("\033[31;1;4mHello\033[0m")

and in Bash you'd use

echo -e "\033[31;1;4mHello\033[0m"

where the first part makes the text red (31), bold (1), underlined (4) and the last part clears all this (0).

As described in the table below, there are a large number of text properties you can set, such as boldness, font, underlining, &c.

Font Effects

Code	Effect	Note
0	Reset / Normal	all attributes off
1	Bold or increased intensity
2	Faint (decreased intensity)	Not widely supported.
3	Italic	Not widely supported. Sometimes treated as inverse.
4	Underline
5	Slow Blink	less than 150 per minute
6	Rapid Blink	MS-DOS ANSI.SYS; 150+ per minute; not widely supported
7	[[reverse video]]	swap foreground and background colors
8	Conceal	Not widely supported.
9	Crossed-out	Characters legible, but marked for deletion. Not widely supported.
10	Primary(default) font
11–19	Alternate font	Select alternate font n-10
20	Fraktur	hardly ever supported
21	Bold off or Double Underline	Bold off not widely supported; double underline hardly ever supported.
22	Normal color or intensity	Neither bold nor faint
23	Not italic, not Fraktur
24	Underline off	Not singly or doubly underlined
25	Blink off
27	Inverse off
28	Reveal	conceal off
29	Not crossed out
30–37	Set foreground color	See color table below
38	Set foreground color	Next arguments are 5;<n> or 2;<r>;<g>;<b>, see below
39	Default foreground color	implementation defined (according to standard)
40–47	Set background color	See color table below
48	Set background color	Next arguments are 5;<n> or 2;<r>;<g>;<b>, see below
49	Default background color	implementation defined (according to standard)
51	Framed
52	Encircled
53	Overlined
54	Not framed or encircled
55	Not overlined
60	ideogram underline	hardly ever supported
61	ideogram double underline	hardly ever supported
62	ideogram overline	hardly ever supported
63	ideogram double overline	hardly ever supported
64	ideogram stress marking	hardly ever supported
65	ideogram attributes off	reset the effects of all of 60-64
90–97	Set bright foreground color	aixterm (not in standard)
100–107	Set bright background color	aixterm (not in standard)

1-bit Colours

You've got this already!

4-bit Colours

The standards implementing terminal colours began with limited (4-bit) options. The table below lists the RGB values of the background and foreground colours used for these by a variety of terminal emulators:

Using the above, you can make red text on a green background (but why?) using:

\033[31;42m

11 Colours (An Interlude)

In their book "Basic Color Terms: Their Universality and Evolution", Brent Berlin and Paul Kay used data collected from twenty different languages from a range of language families to identify eleven possible basic color categories: white, black, red, green, yellow, blue, brown, purple, pink, orange, and gray.

Berlin and Kay found that, in languages with fewer than the maximum eleven color categories, the colors followed a specific evolutionary pattern. This pattern is as follows:

1. All languages contain terms for black (cool colours) and white (bright colours).
2. If a language contains three terms, then it contains a term for red.
3. If a language contains four terms, then it contains a term for either green or yellow (but not both).
4. If a language contains five terms, then it contains terms for both green and yellow.
5. If a language contains six terms, then it contains a term for blue.
6. If a language contains seven terms, then it contains a term for brown.
7. If a language contains eight or more terms, then it contains terms for purple, pink, orange or gray.

This may be why story Beowulf only contains the colours black, white, and red. Homer's Odyssey contains black almost 200 times and white about 100 times. Red appears 15 times, while yellow and green appear only 10 times. (More information here)

Differences between languages are also interesting: note the profusion of distinct colour words used by English vs. Chinese. However, digging deeper into these languages shows that each uses colour in distinct ways. (More information)

Generally speaking, the naming, use, and grouping of colours in human languages is fascinating. Now, back to the show.

8-bit (256) colours

Technology advanced, and tables of 256 pre-selected colours became available, as shown below.

Using these above, you can make pink text like so:

\033[38;5;206m     #That is, \033[38;5;<FG COLOR>m

And make an early-morning blue background using

\033[48;5;57m      #That is, \033[48;5;<BG COLOR>m

And, of course, you can combine these:

\033[38;5;206;48;5;57m

The 8-bit colours are arranged like so:

Range	Description
0x00-0x07	standard colors (same as the 4-bit colours)
0x08-0x0F	high intensity colors
0x10-0xE7	6 × 6 × 6 cube (216 colors): 16 + 36 × r + 6 × g + b (0 ≤ r, g, b ≤ 5)
0xE8-0xFF	grayscale from black to white in 24 steps

ALL THE COLOURS

Now we are living in the future, and the full RGB spectrum is available using:

\033[38;2;<r>;<g>;<b>m     #Select RGB foreground color
\033[48;2;<r>;<g>;<b>m     #Select RGB background color

So you can put pinkish text on a brownish background using

\033[38;2;255;82;197;48;2;155;106;0mHello

Support for "true color" terminals is listed here.

Much of the above is drawn from the Wikipedia page "ANSI escape code".

A Handy Script to Remind Yourself

Since I'm often in the position of trying to remember what colours are what, I have a handy script called: ~/bin/ansi_colours:

#!/usr/bin/env python3

for i in range(30, 37 + 1):
    print("\033[%dm%d\t\t\033[%dm%d" % (i, i, i + 60, i + 60))

print("\\033[39m\\033[49m                 - Reset color")
print("\\033[2K                          - Clear Line")
print("\\033[<L>;<C>H or \\033[<L>;<C>f   - Put the cursor at line L and column C.")
print("\\033[<N>A                        - Move the cursor up N lines")
print("\\033[<N>B                        - Move the cursor down N lines")
print("\\033[<N>C                        - Move the cursor forward N columns")
print("\\033[<N>D                        - Move the cursor backward N columns\n")
print("\\033[2J                          - Clear the screen, move to (0,0)")
print("\\033[K                           - Erase to end of line")
print("\\033[s                           - Save cursor position")
print("\\033[u                           - Restore cursor position\n")
print("\\033[4m                          - Underline on")
print("\\033[24m                         - Underline off\n")
print("\\033[1m                          - Bold on")
print("\\033[21m                         - Bold off")

This prints

ANSI’s Z535.1 standard depicts safety colors that should be used in any kind of public or industrial area. ANSI’s standard colors exist to better the environment around employees and visitors who may come into contact with hazardous material or dangerous situations, and have the general need for clear communication. If properly utilized, these colors are lifesavers in these kinds of environments as they are capable of providing a visual representation of dangers that pose a risk to those nearby as well as alert them to exercise caution. ANSI Z535.1 regarding safety colors is the first out of six subcategories that explain safety symbols, signs, training material, etc.ANSI Z535 ColorsThe standard includes the following colors:Red signifies danger or the need to stop.Orange is mostly used on machines that pose a risk to the worker. This includes crushing, cutting, or general harm.Yellow is used where any amount of caution is needed. This usually applies to common hazards like tripping, the potential of hearing loss, burn risks, etc.Green appears in egress signs to alert people of emergency exits. Green also notates the location of first aid equipment and other safety implements.Blue denotes information on a particular area or item. This color does not have to be safety related.Black and White are often used to direct traffic or alert people about general housekeeping information on the facility.Purple is popular as a radiation color, but that use has not been strictly defined by ANSI yet.Gray does not have a standard use regarded by ANSI currently.The Z535 color standard is recognized by OSHA as a golden standard for use with hazards. However, OSHA hasn’t incorporated the updated ANSI Z535 standards into their mandated requirements just yet. Experts believe it’s only a matter of time until these standards become enforceable by OSHA due to incorporation by reference. Similar Questions What does it mean to have OSHA/ANSI compliant signs?What are the 9 safety colors?What do different colors of safety signs mean?What colors should be used for fire related signs?What ANSI standards have been adopted by OSHA?Why are safety signs important?What are ANSI standards?What are types of signs in the workplace?What are electrical wire colors?Additional Resources OSHA Sign Compliance: ANSI 1967 vs. ANSI 2011 [With 2017 Updates]Safety Colors (OSHA Guidelines and Color Codes)ANSI Z535 [Updated Guide to Safety Signs & Labels]What are ANSI standards?Abandoned Pipe Marking Requirements Under ANSI/AMSE A13.1