In your example situation above, where you're using the 'New Gradient Swatch' dialog box, you have select the little colour swatch at one end and then you can choose from your list of swatches which one should replace it. Do this for each end. You must have the individual colour swatches created in your swatches list already. Once you've created your gradient swatch you can tweak the colour of the individual swatches that comprise the gradient and the gradient will update accordingly. The other way to do it is using the gradient palette (window > color > gradient). Similar to above, with one of the colour swatches at each end of the gradient selected, change its colour by holding Option and clicking on any of the swatches in your swatches panel. But I can tell from your UI that you're on Windows so Option won't be the correct key for this. Try Alt or Control instead. EDIT: I forgot to note that I've always hated how gradients are handled in InDesign but it comes from a place of enforcing a process that is good practice for print work. Answer from accidental-nz on reddit.com