It’s better to have the original file. So you don’t have Photoshop? You can download free equivalents like Gimp or Picasa, and there are plenty of online equivalents, such as
Is there a way to take a gradient image and change the color?
(I was hoping I could tell the computer, “Take this blue gradient and everywhere you see ‘dark blue’ replace it with ‘dark yellow’ and everywhere you see ‘light blue’ replace it with ‘light yellow’”)
Is there a way to take a gradient image and change the color?
(I was hoping I could tell the computer, “Take this blue gradient and everywhere you see ‘dark blue’ replace it with ‘dark yellow’ and everywhere you see ‘light blue’ replace it with ‘light yellow’”)
You can do that with Photoshop, but I’m not sure about other programs. Still, I’m not sure the result would be great, especially on a small image like the one you posted. I’d still much rather do it in the original file.