The light interface of Kdenlive might be in style with KDE, but it is not good for colorcorrection. Hopefully that will be a reality in the future, but I think that the default design should already now be darker - hex #505050 might be a good starting point.
I would also love to see a bit more style added to the interface. If nobody has any objection, I am going to start asking around to some people if they can come up with a design.

The design of Kdenlive needs to be independent of what is used in KDE. What is nice and good in KDE is not necessarily good in Kdenlive. Take a look at MediaComposer, FinalCut and Premiere. As well as all other high end editing and compositing application. They are all a shade of grey. Why? Because of your eyes.
Your eyes are adaptive - actually all senses are. If you hold a blue card in front of your eyes and look at it for a few minutes, then switch it with a white card, it will look yellow. And effects like this needs to be avoided when you work with video and pictures, the same way that you can not mix audio in a noisy environment.