The carbon fiber isn't the part that yellows - the clear coat itself is what yellows over time.
My understanding of gel coats is that they won't yellow for several years if ever as long as they are properly maintained. Clear coated hoods will all yellow over time, but that period of time varies largely depending on the quality of paint work and amount of exposure to the sun.
Your RR hood more than likely came with a very basic clear coat. It will fade over time, but it is fixable. Any paint and body shop should be able to restore it to it's original luster once it has faded.
probably inproper mixture of the gel coat to hardner. the hardner i use is bright greenish blue. only way it can be fixed is if you sand down just about the cf to remove most of the green, then re-layer it with a laminating resin, the clear.