I agree. kddk will be important later on when you really got to go faster. One color per hand will get taxing when you to the really fast things. If you dont know what we are talking about D- left Blue, F- Left Red, J- Right red, K- right blue. D stands for Don which is the sound the drum makes in the middle, and Kat is the sound the outside of a drum makes if you tap it.
Also dont worry about mixing up the notes, its a part of the process. When I was first starting I always hit my red notes on the blue, it stops happening over time. You will find many problems as you keep progressing, but its all temporary. I'm probably not even halfway to being the best and I used to think what I'm doing now was hard. Keep going at it and you will get better and better.