image_blend - blend a color with a sprite
image_blend is a sprite variable that contains the color blended with the sprite. It does not change the color of the sprite to the color blended, but rather tints it. For example, if your sprite was blue and you changed image_blend to c_yellow, then your sprite would be green.
When using image_blend, it is sometimes best to use a gray scale sprite. This way, it will appear as the color blended.
The default value of image_blend is c_white.