I've been looking around for some good Pallet solution for unity, cause sometimes is kind of hard keep every necessary colors for each project in a good place.
Them I found this:
Is a pretty amazing tool to Load / Save / Export Pallet colors, is basically made to work together with the ProBuilder, but can be used wherever you like, I'm using a lot with NGUI:
The amazing thing about this plugin is this little box floating over the scene view, where you will have all your needed colors in hand:
To add new colors is pretty simple too:
If you want more detail, check this video about the plugin: