For fancy dies like floral layering dies I will use colored cardstock and totally overthink the colors (or alternately choose a bunch of colors that result in ugly flowers I don't love because my colored cs stash is small). My takeaway from this video was duh, I should totally try starting with light colored cardstock for stenciled designs like my Create in Quads stencil backgrounds. I almost always reach for white because it's cheap, I have a ream of it, and habit.
ETA it's funny because another video of hers I watched recently was all about inking white die cuts for layered flowers which is also the opposite of what I do. I could cut mountains of white ones and ink blend them with all the beautiful inks I have!
I always start with white but I really love it when people use coloured cardstock for ink blending backgrounds and other technique, so I plan to incorporate that more into my cards now. I definitely see this more and more lately and it's such a good reminder to me to think about more ways to use my supplies.