Well, I still remember when I finally learned how to do selective colouring. I was all cheering and laughing when I finally knew how to do it!
So congrats on knowing (I say, it might be a lot easier for most to learn how to do it than it was for me!).
I say composition of the photos on which you decide you want to apply this technique helps. Like the rose that is supposed to stand out by the colour that you give to only THAT ONE should very necessarily be entirely within the frame and not partly cropped, else your selective colouring will only point out the compositional flaw, no more.