Answer:
Extremely sorry if my answer is wrong or doesn't make sense! Also sorry that I couldn't solve it farther, I solved it using sense and haven't made it this far in math!
Explanation:
If red is 2:3 then that means red to green is either 2:2 or 2:1. Same goes with blue.
If green is 6:19 then we can figure out the 2 possibilities for red to green.
First Possibility:
If the red to green ratio is 2:2, then the red to green to blue is 6:6:13 because 6 + 19 - 12 = 13.
Second Possibility:
If the red to green ratio is 2:3, then the red to green to blue ratio is 4:6:15 because 6 + 19 - 10 = 15.