I hope you mean exactly the light if you hit a note. If so, follow this: in your skin folder should be "LightingL" and "LightingN". Take these, make them transparent and put them back to your skin folder.
If you would put them out of your skin folder, it would be replaced by default. That's why we make some elements transparent.
How would you get rid of the hit lighting for mania because I tried both ways and the skin I use doesn't have the LightingL or LightingN and I tried to download the file but I couldn't put it on osu so is there another way to remove the hit lighting for mania?