Here are two seedlings from a cross of Tweety Bird X Orange Design,
Both have yellow standards and orange falls. Both of these seedlings
have four "t" genes, so have the genetics to block the conversion of
lycopene to beta or alpha carotene, yet have yellow standard that are
have carotene, either beta or alpha carotene. Usually we only get
lycopne when the up conversion of lycopene is blocked, yet we ave both
lycopene and one of the prominent pigment carotenes present.
The orange falls are a combination of the same carotene seen in the
standards plus lycopene to produce orange. The one seedling may also
have some anthocyanin in falls to provide a darker orange. I do have
some seedlings from this line with some interesting colour combinations.
I refer to this yellow as the alternative yellow as it appears to be
recessive, unlike regular carotene yellow., so would appear to have
some different genetics involved.