This is what we do, too. I read the word, use it in a sentence; when he tells me he's ready I look at his paper. If it's correct I tell him good job, and carry on. If it's wrong, or a new pattern, then I write it. When we began the program and I was writing every word, a lesson took 20 min. Now it's about 10 min.
The use of two or more colours is mentioned in Right Brained Child in a Left-Brained World and I sat in a brain research seminar that mentioned this as an effective memorizing strategy, so we do that. I also see that patterns get learned almost incidentally, such as 'drop the -e and add -ing'.
My .02