Recently, colored arcana books were introduced that when used, set a caster's Magic Missile to a certain color (blue, pink, red, rainbow etc).
For even more flavor, make it so that the Light cantrip works the same way -- instead of being locked into its default light color, it too takes its color from the arcana books when used.
The existing ability to cast Light not just on yourself but on other PCs, but also on placeables etc makes this a flavorful opportunity to create spooky/cool/themed and magicky & wizardly ambience for casters.
For even more flavor, make it so that the Light cantrip works the same way -- instead of being locked into its default light color, it too takes its color from the arcana books when used.
The existing ability to cast Light not just on yourself but on other PCs, but also on placeables etc makes this a flavorful opportunity to create spooky/cool/themed and magicky & wizardly ambience for casters.