PNG's suck

Being an artist, a good variety of art in this game is important to me - I want there to be hundreds of unique horse pictures. Rather spending 20 years to individually make all of these, I have opted to use PNG's and their support for transparency so that I can layer white markings on top of base images in combination. Pretty cool. Problem: I have noticed that in the browser, my brown and chestnut look almost identical. In Photoshop they look great, very clearly brown and red, but in the browser everything is desaturated! This turns out to be a problem inherent in the PNG format; without getting too technical, they have issues displaying the correct gamma in a browser. I found a program to adjust the gamma such that my images don't look quite so desaturated, but it's still a problem. I may have to convert my base images to JPEG and just have the markings be PNG. Not a huge loss, but it does mean forgoing the ability to customize the background on the fly...