I just realized it would be really nice and very useful to have a colour grading effect in Kdenlive. Colour grading is used to automatically get all of the clips in a movie to get the same colour tone.
Don't really know much about the math but in most other applications it works by selecting the darkest and brightest spots in each two clips.

Just thought it would be a really nifty idea.

Cheers,

Well color grading is about a lot more tgan matching two clips, which may or may not be what is wanted, but kdenlive already some of those tools including decent luma waveform, RGB parade and histogram. SOP/SAT tool and numeroud others.

No auto match with some sort of histogram equalization algo, sure but that really isn't color grading just primary color correction in a rather lazy way. ;-)

Only downside currently is that color processing is at 8bit precision rather than 32bit, but generally useful all the same.

As you talk about color grading, a dithering effect based on gradfun would be useful to deal with the 8 bit limitation mord easily.

On topic: Kdenlive already has color correction and grading abilities and I think what it provides is far enough for most users. Automatic correction would in fact not work that well on different clips and you would have to do manual correction either. That would take more time than simply do your primary color correction with curves, hsv and brightness/contrast using scopes.
The main disadvantage of kdenlive for grading is it's linear effect workflow. For example you cannot split a strip's HSV space up and so modify the Hue and Saturation independently or do some layered combination of effects without doing timeline mess. That would only be possible with a node based grading system which is totally different from how kdenlive works.

You can modify hue and saturation separately with the "hue shift" and "saturation" effects.