I agree with you on the yellows. He is from a Ghost Mojo to a Bumblebee het Ghost, so I thought he may have grabbed the Pastel gene as well. The both parents are very high quality and the Bumble Bee did not brown out in adult hood. But, Ghost Pastaves seem to have more white on the head. He does have great blushing and color.
I have also considered mixing in either a Hypo Citrus Pastel or a Hypo YB to really amp up his color. Kinda sounds weird for a Hypo/Ghost project, but I think it would be sweet.