I believe I’ve figured it out; I have House Finch and Purple Finch regularly visiting my feeders. Sherrie tells me House Finches "are EXTREMELY variable", so perhaps that is why some are redder and some International Orange, like this guy.
These photos are not mine, and appear on each bird's profile page on the links I've provided..but are wonderful illustratons of the three (?) birds I see here.
They really do seem, to me, to be quite similar…but the Purples have an all-over pinkish tint to them and are nowhere near as stripy.
While the female Purples look like little winged ground-squirrels with their brown and white markings, the females that could be Cassin’s puff up their topknots just like the males, like this female Cassin's is doing here.
Here is a fascinating discussion on the three birds and how to Distingush the Differences. Lovely birds, all.