Turns out this piece of code from the matplotlib examples gave me the answer I was after.

The hex codes of the "tableau" palette are as follows:

tab:blue : #1f77b4
tab:orange : #ff7f0e
tab:green : #2ca02c
tab:red : #d62728
tab:purple : #9467bd
tab:brown : #8c564b
tab:pink : #e377c2
tab:gray : #7f7f7f
tab:olive : #bcbd22
tab:cyan : #17becf

Using the following code I made a dictionnary containing all the named colors and their respective hex code :

import matplotlib.colors as mcolors


mcolors.TABLEAU_COLORS
mcolors.XKCD_COLORS
mcolors.CSS4_COLORS
#Base colors are in RGB so they need to be converted to HEX
BASE_COLORS_hex = {name:mcolors.rgb2hex(color) for name,color in mcolors.BASE_COLORS.items()}


all_named_colors = {}
all_named_colors.update(mcolors.TABLEAU_COLORS)
all_named_colors.update(BASE_COLORS_hex)
all_named_colors.update(mcolors.CSS4_COLORS)
all_named_colors.update(mcolors.XKCD_COLORS)


#print(all_named_colors)
print(all_named_colors["tab:blue"])
>>> #1f77b4

You can color the tabs with openpyxl by using RRGGBB color code for sheet_properties.tabColor property:

from openpyxl import Workbook

wb = Workbook()
ws = wb.create_sheet('My_Color_Title')
ws.sheet_properties.tabColor = 'FFFF00'

wb.save('My_book_with_Yellow_Tab.xlsx')

You can try creating a custom theme.

import tkinter as tk
from tkinter import ttk

root = tk.Tk()

mygreen = "#d2ffd2"
myred = "#dd0202"

style = ttk.Style()

style.theme_create( "yummy", parent="alt", settings={
        "TNotebook": {"configure": {"tabmargins": [2, 5, 2, 0] } },
        "TNotebook.Tab": {
            "configure": {"padding": [5, 1], "background": mygreen },
            "map":       {"background": [("selected", myred)],
                          "expand": [("selected", [1, 1, 1, 0])] } } } )

style.theme_use("yummy")

note = ttk.Notebook(root)
f1 = ttk.Frame(note, width=300, height=200)
note.add(f1, text = 'First')
f2 = ttk.Frame(note, width=300, height=200)
note.add(f2, text = 'Second')
note.pack(expand=1, fill='both', padx=5, pady=5)

tk.Button(root, text='yummy!').pack(fill='x')

root.mainloop()

EDIT

The most detailed ttk documentation is from the tcl/tk world

eg.

http://www.tcl.tk/man/tcl/TkCmd/ttk_notebook.htm

For some useful python-based examples, you can grab the pyttk-samples package from http://code.google.com/p/python-ttk/

Your question has more to do with ttk style Custom.TNotebook than canvas.

One way to achieve the effect is to create your own theme.

'mytheme' defines new values for Scrollbar, Frame and Notebook.

import tkinter as tk
from tkinter import ttk

master = tk.Tk()
# Create your own Style theme
style = ttk.Style(master)

# Define your color scheme
RED = "#ff0000"
ORANGE = "#ffa500"
YELLOW = "#ffff00"
TROUGH = "#668877"

style.theme_create(
    "mytheme",
    parent = "default",
    settings = {
        "TScrollbar": {
            "configure": {
                "background": YELLOW,
                "troughcolor": TROUGH,
                "lightcolor": ORANGE,
                "borderwidth": 1},
            "map": {
                "background": [("active", ORANGE),
                               ("disabled", YELLOW)],
                "arrowcolor": [("active", YELLOW),
                               ("disabled", ORANGE)]}},
        "TFrame": {
                "configure": {
                    "background": RED}},
        "TNotebook": {
            "configure":
            {
                "background": ORANGE}},
        "TNotebook.Tab": {
            "configure":
            {
                "background": ORANGE},
            "map": {
                "background": [("selected", RED)]}}})

style.theme_use("mytheme")

master.rowconfigure(0, weight = 1)
master.columnconfigure(0, weight = 1)

tab = ttk.Notebook(master)
tab1 = ttk.Notebook(tab)
tab2 = ttk.Notebook(tab)
  
tab.add(tab1, text = "Tab 1")
tab.add(tab2, text = "Tab 2")

# changed place manager so tkinter can calculate master size.
tab.grid(row = 0, column = 0, sticky = tk.NSEW)

#tab 1
a = ttk.Frame(tab1)
# canvas needs scrollregion and remove all surrounding space
canvas = tk.Canvas(
    a,
    background = RED, highlightthickness = 0,
    borderwidth = 0, scrollregion = "0 0 1000 1000")
# important! pack canvas
canvas.grid(row = 0, column = 0, sticky = tk.NSEW)

scrollbar = ttk.Scrollbar(
    a, orient = tk.VERTICAL, command = canvas.yview)
scrollbar.grid(row = 0, column = 1, sticky = tk.NS)
# important! connect canvas to scrollbar
canvas["yscrollcommand"] = scrollbar.set

b = ttk.Frame(tab1)
tab1.add(a, text = "X")
tab1.add(b, text = "Y")

#tab 2
c = ttk.Frame(tab2)
d = ttk.Frame(tab2)
tab2.add(c, text = "A")
tab2.add(d, text = "B")

master.mainloop()