Hi Kristy,
Doesnt seem to be much traffic in this forum any more. Im no expert but from what I read, there are about 400 species of Ixora, but only a few are grown in cultivation, and those ones mostly form the basis for the cultivars which have resulted in so many different colours, and sizes, such as the dwarf forms. So I think the colour thing is more a genetic thing, with that part of the plant perhaps trying to revert to the colour of one of the plants which was a "parent" in the hybridising process. I dont believe the proximity of your Prince of Orange has anything to do with it as the flower colour would be determined by your own plant, and cross-pollination would only affect a prospective offspring - new plant - arising from seed. The appearance of 5 petals is a mystery tho, since all the pics of Ixoras including a few of the species, seem to indicate 4 petals as the norm. So you may be "on" to a natural "sport" or variation there. Remembering that new cultivars can be developed a few different ways, I would be preserving that shoot of your Ixora, certainly. I believe that any seeds it produces would be unlikely to grow "true" - even to the dwarf yellow, since its probably a cultivar any seedlings could turn out anyway. My limited understanding is that this variation would need to be reproduced vegitatively - by cuttings - and grown on into a new plant, and that process might need to be carried out several times to isolate whatever new"gene" you have, to ensure that this colouration or petal thing, is consistent and reliable. Much the same way people with a variegated leaved plant on a plain one, keep promoting the variegated one and cutting out the other. If you are interested (why not) then you may be able to get onto a nursery which would be interested in assisting you more. One of my searches brought up this website relating to Ixoras in thailand and as they originate in SE Asia I thought it might give you a bit more background on the species and some of the more common cultivars. Anyway, good luck! | 
