If you want to make a color palette in Photoshop, I have this blank palette template that you can use. The white and black are the basics I always use, neither are pure white or black so that I can add texture to them if I want.
Then lock the new layer so you can recolor it cleanly.
Zoom in to a pixelated view of the image to select just the right color.
Continue until you have all the colors you want. Save as a .PNG file to preserve the hard edges and color.