This function controls the blending (or "tinting") of the background sprite and the default value is -1 (which represents the constant c_white, which can also be used). Any other value (including internal colour constants like c_red, or c_aqua) will blend the specified colour with the original sprite. You give the background element ID (which you get when you create a background element using layer_background_create() or when you use the function layer_background_get_id()), and then set the blending colour to use. Below you can see an example of a sprite that has been blended with different colours: Please note that you should try to limit blending on the HTML5 platform (unless using WebGL), as each blended sprite has to be cached separately and so having many blended sprites may adversely affect performance (you can also set the cache size using the function sprite_set_cache_size()).
Argument Description background_element_id The unique ID value of the background element to change blend The colour to blend with the background sprite (default is c_white)
var lay_id = layer_get_id("Background_sky");
var back_id = layer_background_get_id(lay_id);
The above code gets the ID value of the background assigned to the layer "Background_sky" and then tints it to a colour.