|You're not allowed to use selection tools.
But you are allowed to use the selective color adjustment layer. That's what he meant by "selective color adjustments." Either that, or the shot will be DQd during validation.
That adjustment layer is named a bit confusingly for purposes of DPC rules. But what it does is "whole image" editing. Specifically, it changes every pixel of a certain color you choose in a dropdown box in the same way. It's the same as using a levels or curves adjustment layer, which affects every pixel of a certain brightness or color channel in the same way.
I find the most useful way to use it is to add more black to the blacks, but it's also useful to make other changes.
As for you thinking there's no red to enhance, I disagree. You'd be amazed at what colors lurk in your pictures if you push things to an extreme. In my Wealth entry, for instance, the brilliant pink in the lower left was a barely visible smudge in the original: