Screen widgets with transparency are darker when displayed in an HTML5 environment

If the user creates a widget blueprint and adds an image with transparency the image will appear slightly darker when launched in HTML5 (firefox nightlie in this test)

1. Open First person project
2. Create a new Widget blueprint
3. Add an image to the designer tab
4. Change the color to yellow
5. Set the transparency to .5
6. Add the widget to the view port
   Open level blueprint > begin play > create widget > add to viewport
7. Play in Editor
8. Walk up to a wall so that there is a solid gray back ground
9. Take a screen shot
10. Stop PIE
11. Launch on to FireFox nightlie
12. Walk up to a wall so that there is a solid gray background (the exact same spot as before)
13. Take a screen shot
14. Compare the two screen shots in a program such as paint (In the attached image the top half of the HTML5 screen shot was placed over top of the PIE screen shot)
15. Notice that the HTML5 is darker than that of the PIE version

[UMG] - Muddy Semi-Transparent Rendering