Richard Bonser kindly emailed me the following email he received from Morten relating to House Finches in captivity in Continental Europe..........
My brother Jacob and I have been in the "cage bird business" for more than 20 years and have a reasonable knowledge about bird occurences in European bird shows. The American or Mexican House Finch is very common at the moment with probably thousands of bird in captivity in Europe. We both recently visited the colossal cagebird marked in Zwolle (The Netherlands) and House Finch was pretty commonly offered for sale or advertised there.
House Finch has, like the other carpodacus species, difficulties with keeping the red colour in captivity and therefore at least 90% are actually yellow variants. Jacob and I have both kept Pallas's Rosefinch, Common Rosefinch and 'Mexican' House Finch and if you don't feed them on a certain diet, they will lose the red colour and turn yellow or orange-yellow (Morten)