Yippee! My new blue (bottom) is pretty much dead on the old blue (top). And not too much tinkering was needed to get it there. I did have to do one more abrash than I had planned, since it was a bit lighter. But in the end, when it was dry, cut and mixed in with the other strips, you can't tell the difference.
Feeling confident, I then proceeded to overdye and abrash a light ochre value that I had dyed and never used in the rug. And this was equally as successful. I even anticipated that the original colour had a bit less bottle green in it, so added that to the abrash forumula - and eureka - it's a match.
I guess this dyeing thing is like everything else in life. Practice makes perfect. And as long as this isn't going to be the last rug you ever hook, you will find a place for all the little "accidents" you create.
In addition to feeling much more confident about my dyeing prowess, I have discovered something else about myself. Despite earlier indications that this would be the one and only Oriental rug I would ever hook, I find myself looking at larger ones. I guess the richness and sheer splendour of these masterpieces is enough to win over a dyed-in-the-wool primitive hooker.