There's not one single case in the world where a red suffused bird has produced red suffused young, so it can never be classed as a mutation.
It is commonly a genetic alteration where the yellow psittacin in the feathers turns red, for an unknown reason. It's been seen in eyering and peachfaced species. Some are born with the colour and lose it, some develop it at an older age and die! I myself had a personatus born with a red collar, it lost the colours during it's juvenile moult though.
The atlas, whilst a wonderful book to own, has alot of out dated information which due to research over the past decade, is proven inaccurate. The redino is a prime example.
