I see what you're using blend effects and force texture on layer which uses firework particle. You did it wrong, there a solution, background doesn't require to force own texture, only it does to particle object with effect destination out and layer is NOT transparent and forced texture.
There a fixed .capx
http://dl.dropbox.com/u/76227787/ForcedTextureFireworks.capx
Also remind force texture feature MAY consume the majority of CPU, there a workaround to save performance, you must create separated particles with different colour, make an sprite acts as spawner, it's invisible and generates 1 each firework with different colour, also create an global variable, its value is 0. System creates an spawner sprite on mouse position, spawn is on created, set variable value is "choose(1, 2, 3)".
1 = blue
2 = red
3 = green
Besides if global variable is 1, creates blue fireworks on spawner position, then spawner gets destroyed and set 0 to blue variable when it's done. I hope it helps you.