House Finches
House Finches are one of the more "common" birds in most of the US (their history is rather fascinating, here is a good article about it), but even they can be confusing to birdwatchers, and that is mostly due to the variety of colors in the males. It can range from faint blushes of rose to vibrant reds with pink hues and even orange. Their color and vibrancy depends on their diet. The ones I see are usually reddish but yesterday, there was also an orange one. He looked especially cool in the gloomy light.
Because of the variety in color, sometimes people mistake House finches for Purple Finches. There are some features that can help to differentiate them. I made a chart last year to help with that, which I am posting below too.