The decals are (like many kits from this era) yellowed. Making replacements is not a problem, but if the artwork isn't bad, even if it is a bit dated, I like to try to build these kits using what comes in the box.
These have been taped to the inside of a window in my shop that gets direct sunlight for most of each day to sun-bleach them for two weeks.
Both the clear and the white benefited from this.
I'll put them back on the window until they are needed just to get maximum results, but this is possibly as bleached as they will get.