I have 2 polygons drawn over the same points, where one of them is red and the other is green.
However, sometimes (randomly as far as I can tell) their colors just blend together, even though they both have their alpha set to 1.0 and translucent to false. Other times they seem to be just fine.
Here is a fiddle with a demo of the problem, which as I said, sometimes work and sometimes it doesn't.
Am I missing something?