Light Filters?

I'm new to rpg maker, and I was hoping to make a game with a darker tone, and I was trying to avoid having to replace all the tilesets I was using. I don't know if this is possible, but are there any ways to filter lighting or changing the lighting effects.

Yami's overlay allows you to use images over your map to add light, shadows, and even tiles.

If all you wanted to do was make maps darker you just have to use the shadow layer.

http://yamiworld.wordpress.com/yami-engine/image-display/overlay-mapping/

Moved to general support (you didn't specify which maker you are using and you posted in the wrong forum)

As to your question, you can either

A) Darken the tilesets yourself using a simple image editing program, or

B) Use the tint screen event command.

Thanks, I'll make sure I give these a try. And, sorry I put this in the wrong place!