Tint your images in ImpactJS on the client side. Uses the 'multiply' blending mode to colourize each pixel.
(example sprite from http://opengameart.org/content/zombies-skeletons)
- Copy imageblender.js into your lib/game folder
- In your game's module, add an entry to the require section for the module 'game.imageblender'
- Append #hexcolor to the path in any ig.Image or ig.AnimationSheet. For example, rather than loading 'media/monster.png' you can change it to 'media/monster.png#FF0000' (Or '#F00') to tint it red.
For more info see this forum post