Someone posted this on Carolina Birds on Facebook. He photoshopped it to put all these types of finches on it. I'm sorry I do not know whom to give proper credit to.
Supposedly we may get siskins and purple finches this year. I haven't seen a purple finch in twenty years - it would be a joy to have some at our feeder.
Roger Tory Peterson always said that a purple finch (lower left in picture) looks like it is dipped in raspberry juice. That's a perfect description of that little bird. The house finch is more red/orange, and its red is restricted to face/front and rump. The color is more distributed on the purple finch.
I do not think I would be able to distinguish the difference in the female purple and female house finches.
I would love to get siskins and purple finches this year.