You buy the LEDs for the specific frequencies you need, notably red and blue. All other colors are filtered out by the chlorophyll in the algae of the polyps.
BTW our eyesight is more sensitive to green, so those other 2 colors would look dim to us if power was equal between RGB LEDs.
It's all about IP. It wouldn't be horribly difficult to put a GPU and CPU on the same die. BUT, Intel doesn't GPU manufacturers getting into the x86 business and GPU makers certainly aren't going to give Intel any of their technology and get cut out the market. Intels attempts at GPUs has been less than spectacular. Good enough for Word and Excel. Not good at modern gaming.
So for the foreseeable future CPUs and GPUs will be treated as seperate entities.
Where there's a will, there's a relative.