There’s no official solution unfortunately, some skins were forbidden in competitive because of this specific limited visibility.
If you know how to manipulate Variables.txt file where the game settings are, you can further disable ALL shadows including the blob/circle ones under that are usually left by the game’s low setting. Customization here is pretty intuitive and it carries over to the game. Something with the Lighting/Shadow interaction - nothing to do with gamma or other presets. This way even with low graphics you can have that perfect spell display. Floor textures, bushes and expecially zerg creep might end up looking awkward.
The settings have changed names over the years and I can’t pinpoint the exact line, but no doubt you can find it somewhere on the internet. If you get something wrong your game may not run correctly or you may experience graphical problems. Simply delete the file and the settings will go back on default if you mess something up.