How does the cannon game keep score?

Question here from Gorman Swiftmancer of The Necromancer's Doctrine:

How does the cannon game keep score to give you your points at the end?

Hmm, I looked around and I couldn't see if anybody had answered this question yet, so I ran a few test runs:

3 black = 0
2 black, 1 blue = 1 point
1 black, 2 blue = 1 point
1 black, 2 red = 1 point
3 blue = 1 point
2 blue, 1 yellow =2 points
1 black, 1 blue, 1 yellow = 2 points
1 black, 1 red, 1 yellow = 2 points
1 blue, 1 red, 1 yellow = 2 points
1 blue, 2 red = 2 points
3 red = 2 points
1 blue, 2 yellow = 3 points
2 red, 1 yellow = 3 points
1 red, 2 yellow = 4 points
3 yellow = 4 points

As far as I can tell (I ain't the best at the maths), the points seem to be calculated like this:

Yellow = 1.2 points
Red = .7 points
Blue = .4 points
Black = .1 points

And then all numbers are rounded.

Something like that. That may not be 100 percent correct, but it's the best I can do at 6:00 am in the morning. :-)

Happy Dueling!