Well, it would of course be possible. The question here is whether this is acceptable visually (and I am not sure whether completely customizable colours are a good idea in the first place). Colouring the bars completely would certainly be very susceptible to colours that are off with regard to other colours used by the frontend and other users. The probability for that would increase with the number of users.

But the idea of making it easier to identify the owner of a task is generally a good one. We do have plans to redesign the UI of Kunagi completely to make it more up-to-date visually. That is probably where such UI changes would fit in conceptually. Due to low manpower at the moment, however, I don't really dare to estimate when this change will occur.