If these look like sparrows dipped in raspberry juice you may be seeing one of two types of birds The House Finch or the Purple Finch.
here is a purple finch
http://www.sialis.org/images/purple_finch005.jpg
and here is a house finch
http://www.terrierman.com/housefinch.JPG
They often flock in with the more usual sparrows making for quite a colorful surprise.
Info on these birds here
http://www.birds.cornell.edu/AllAboutBirds/BirdGuide/House_Finch.html
http://www.birds.cornell.edu/AllAboutBirds/BirdGuide/Purple_Finch.html
The purple finch is a native species and the house finch was introduced to the US.
A smaller bird with red markings is the Red Poll
http://www.birds.cornell.edu/AllAboutBirds/BirdGuide/Common_Redpoll.html
I think the pine grosbeak, another sparrow looking bird with red coloring, which you can see here
http://www.birds.cornell.edu/AllAboutBirds/BirdGuide/Pine_Grosbeak_dtl.html
lives too far north to be seen in your area.
Hope this helps you!
I think you may have mistaken the species. Females of the purple finch and house finch look very plain in comparison to the males. This is called sexual domorphism where one sex looks very different from the others.
So you may have seen very plain oridnary brown sparrows raise up ones which are red toned because they are males.
Another possibility is that these birds are hybrids of some sort. Perhaps not of wild birds but escaped fancy cage finches that interbred successfully with the local finch population. Inbreeding could bring the color back out if one generation looked plain the next if the hybrids interbred might look fancier.
And of course mutations are a possibility and again interbreeding of birds with a color mutation can result in a larger population with a color shift.
In some areas for example you see a higher incidence of albino birds or animals due to the successful breeding of albinos with regular colored ones.
Wild Bird Expert
Rehabbing wild birds, raising nestlings, study and observation of many species