The first suggestion would be quite useful but will need to wait for the next larger release. I´ll put it on our list.
The new colored boolean icons in list fields are fixed, so there is no direct control over them. For your own icons, we force them to be black and white so that they can work with different color/display options that the user can choose.
We could build a system where the author would decide on a prefered color and the system would colorize the icons in the context of the current display settings (apply/remove contrast, adjust hue and so on).