How to deal with Enchantments outside of G/W?
Enchantments are permanents, so they can also be destroyed by spells or abilities that destroy permanents

There are several non-G/W cards that destroy certain types of permanents, rather than enchantments specifically: Gatherer

You can also make your opponent sacrifice certain types of permanents, although that of course leaves some degree of choice for your opponent, depending on the board state: Gatherer

Generally, you should accept the fact that enchantment destruction is firmly inside the G/W part of the color pie, and you should look to less direct ways of dealing with enchantments. 

As for direct answers, your best bet outside G/W are Blue counterspells and bounce effects for tempo, and sweeper artifacts.