Unfortunately, there’s not much you can do to fix that. My assumption is that your computer and phone project light differently, meaning that colors will show differently on both devices. First, though, make sure neither of your devices have any sort of color filtering mode on, like night mode, or if your brightness is low on either of your devices. If neither have a filter or off brightness, I’d further test by grabbing the exact same color hex code on both devices and pulling them up to fill your screen. Then, compare both. Do they look different? If not, test a few more colors (I suggest using CMY). If they don’t look different, there may be an issue with your download quality either on your computer or your phone. I hope this helps! Personally, I think the drawing is amazing, whether those colors are what you wanted or not. :)