This post contains a bunch of colour palettes you can use in your games and pixel art projects, as well as some resources for helping you to automatically generate or manually create your own palettes, as well as some other resources. Updated periodically as I discover more stuff.
If there’s a colour you want to change in multiple places in your image, this tutorial will teach you how you can do that in Photoshop with ease. There are 2 possible ways. This tutorial is aimed at Pixel Art.