Allow RGB input for min and max color

[criticalfx]

I have an RGB bulb and an RGB LED strip by the same manufacturer that don't match in color when using Kelvin values for min and max. They don't match even if I select prefer_rgb_color.

It would be neat to be able to input RGB min and max values for this reason.

[funkytwig]

RGB offsets seem a better solution, I like this idea but there are already heading for too many parameters IMHO. Which manufacturer and which lights? How much are they out by, maybe a picture showing both fixtures. Bear in mind different fixtures from the same manufacturer may use different LEDs.