I agree with S.E. Go back to your natural colour, then let em be. Dyes do dry out the hair , that is why they give the heavy duty conditioner with it, but for dreads you must skip that step, therefore your dreads will be dry, maybe getting brittle with prolong dying. If you are planning to keep your dreads for years, I would do it only one last time. With a regular hair style, it gets coloured/dyed, grows and then gets cut. Eventually you will have new healthy growth that you can cut to. With dreads, they grow, but we don't cut them. So the dried section are still there.
If you are not planning to keep your dreads for years but as a funky style at the moment, then I say have fun with them and add splashes of colour or wraps, whatever. Girls just want to have fun. You can get back to healthier new growth hair when you.....gulp.....cut them. Peace