I'd like to have the ability to define complete palettes and switch between them. I suggest getting a graphic designer involved in creating some defaults. As a visual tool, the colour language involved has a significant impact upon the customer's impression of quality. The default 'pastel rainbow' scheme is reminicent of mid-2000's era enterprise software so has the effect of dating the application in the customer's perception.

I'd suggest considering some optional styles to add graduations or subtle colour shading to the cards to help modernise the look as well.