yellow v blue flowers query

[nytecam]

Could someone explain why some cultivated plants having a range of flower colour but typically have one colour missing eg usually yellow or blue? I'm sure you know many examples

I've asked this query many times down the years and been told somewhat obviously "It's in the genes" but I'm hoping for a more lucid explanation. TIA

[artdemole]

It is all to do with Phytochemistry. Flavonols or Carotenoid oxides are responsible for cream/yellow flowers. Whilst Anthocyanin results in other colour mixes.
Have a look at jxb.oxfordjournals.org This was published 1952 and give breif description. Hope it helps.