Would it be possible to add a gradient creation tool? Maybe like a panel to define gradients which could then be selected in the color tool? Here's what the panel could look like:

Type would give the user the option to have either a linear or a radial gradient.

Steps would be a table where the user picks the progress percentage, color, and opacity. 

Defined would be a table that shows a preview of the gradient in a cell. Gradients are added from a button above that creates the gradient specified in the steps.

That's quite a lot of work, and I'm not if I even have the programming/UX skills to make something that doesn't feel too clunky. But I will give this a look :) It'd be a fun tool to have.