As Kiki has mentioned above, make sure to export using .png since quality is much better than .jpg, just remember to change the file type in y'er .cgf file as well so the preset shows up correctly in the Preset Maker.
What I'm seeing that may be the issue is the pixels. It looks like ye used the pencil tool to make y'er preset, which shows up pixel-like and can sometimes cause discoloration. If y'er not going f'er a pixel look, try using the blur tool and smooth out the edges of the markings to see if that fixes the issue.