I've had a better idea, I can set sun_color to blue instead of using a sprite, so te red colors of the enitities will be seen

in case of texture it will be very weird, because the colors red comes from the inside, when the person is in front you see red, but when its left, you see red inside but on the surface its not red..

I think you need a shader, that has some kind of fog oulining the surface or something.
depends on the project.

you're right, but in free version i can't use shaders, so i need to do it in another way