You can change the "steps" variable to control the strength of the light. The default is 20, which makes a 20*8 or 160 pixel radius light.
Color light is probably done the same way you'd color lights with the shadow caster.
Here's one way that doubles the amount of objects. Basically a layer to do the shadow, and another layer with the light color which is blended with the scene. This also animates the color and strength of the light.
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Multiple lights would be done by doing each light separately and combining the shadow and color layers of each. As is the performance isn't good enough to do that. Also I'd want to reintroduce something like paster to handle the mixing instead of juggling layers.
It's as far as I'll go with this for now. A significant speedup can be done by doing the floodfill algo with javascript, and the drawing should be simpler/faster to draw directly to textures for the shadows and colors. Less overhead at least, not my cup of tea to do that mixed with construct though.