Colouring the Butterflies
Right click the Butterfly in the Objects Window again, and add the Tint Effect. Then go back to the Event Sheet and add some more actions to happen when the Butterfly spawns (I did this in a blank sub event to keep it neater).
I fancied some pink and purple butterflies, so here are my values and their result:
Now you can take this a step further, and make a bigger variety without the weird brown colours in the middle. Give the Butterfly an instance variable, call it Colour (or Color if you're going to be like that).
When the Butterfly is created add another action, set the value of Colour to random(0.10).
Now make a sub-event of that event, and make the condition If Colour less than or equal 5, and another If Colour greater than 5 and give each sub-event different RGB values. Here is what I entered, and my results.
Woot now you have some lovely random butterflies to add to your background! And the method works for other things, such as snowflakes or leaves: