Norfolk,
United Kingdom 
I purchased, from a nursery not GC, about a 100 Pyracantha plants a couple or three years ago. They were to go along the front of the garden to cover a rickety low boundary fence near the road. With great care with the labels I planted them alternatively red,orange,yellow berries with the idea they would look pretty! This year they are full of berries - all orange, they were different last year! So.. is it because they pollenated each other and the orange are dominant (but they are plants not seedlings!) or do they revert anyway?
20 Nov, 2014
Answers
Cross pollination wouldn't change the berry colour. That's something in their genetic makeup, and it can not be changed.
Cross pollination may change the colour of the next generation, but the parent plants would stay as they are.
Maybe the yellow and red ones haven't produced berries this year .... and if the branches have grown in between each other, it would be difficult to tell which plants the berries are on.
It must be disappointing for you though :(
21 Nov, 2014
mm I've seen this problem before, but I didn't care because they weren't mine and they looked quite nice, maybe its a genetic mutation or an adaptation, after all evolution still continues.
21 Nov, 2014
I have to say that some of the varieties begin with orange berries and they eventually turn red. Perhaps give them time.
21 Nov, 2014
Thanks for your replies to my question. I think Hywel may have got it right and the original coloured ones are the only ones fruiting this year and have intertwined making it look as if they are all orange. I expect the original are more vigourous anyway and when they were smaller I did twine them in and out to fill the spaces. Last year I am sure I had all the three berry colours and couldn't really see how the plant itself would change, it's just weird. They will have no chance to change colour later as they are being eaten pretty fast. They were grown to provide food for the birds later in the year, but it looks as if they are being eaten by yet more mice! I would assume that birds ate them whole, but while trimming the top (so we could see to get out of the gate) most of them have been 'chewed' and the ground is covered with tiny bits of berry. Anyone know if this would be mice? I know we have loads of little holes in the gardens near the big hedges and edges of the lawns, so again assume they are mice, voles or shrews. Mustn't complain as the hedge is pretty anyway and we won't get the owls unless we have the critters for them!
22 Nov, 2014
I suspect it might be due to cross pollination but I have 2, a red and yellow one within 6 ft of each other and they stay true to berry type.
did they berry correctly ever? and how were they different last year?
21 Nov, 2014