So i will explain how i came across this Color Picker feature.
The sites we develop these days have some really crazy colors which you dont normally get in the color picker. So there was a scenario where the page had text that was configurable from a SharePoint List using a Multi line Rich Text Editor Textbox. And the text colors were following a theme.
So we needed to provide these colors in the color picker for users to easily apply the color on the text without needing to find out the RGB or HEX code.
here is what i found that worked for me.
-ms-color:"Theme 1"; /* This will appear as tooltip */