I reckon it probably only goes to 99.0%. Otherwise, if you were on say 99.3% then couldn't you use another green for the extra 0.6% or 0.7%? (kind of like the rare occasion that boosting morale from very good to superb requires two blues instead of one*) However, whenever you're on 99% you can't use any more greens, you're on the maximum.

On a side note, I don't know why it stops at 99%, surely it should go to 100%? I suppose that's probably one of the reasons one might think it does go to 99.9% (or actually 100% but displays as 99%), it would be strange to stop at 99.0%. I still think it does though.

* in that case, don't bother with the second one, it only adds less than 1% from memory from the old version (like from 99.x to 100 or 98.x to 99)