Is it possible to do localised colour correction similar to that described in this link with Kdenlive? Can anyone recommend a good tutorial?
Yes, it can be done.
The first part, (the high/mid/low "wheels"), you can do with the curves effect, see:
But I guess your are mostly asking about the second part, the "secondary correction".
This you can do too, although no tutorial has been done on this yet, AFAIK.
It goes like this:
You put your clip on two tracks, one copy below the other.
Next, you apply ANY filter you want to one of the copies.
And last, you apply a composite, and adjust your selection (alpha) so that the changed track shows only in the regions you want to change.
To select the red bucket, for example, you could use the "Blue Screen", or for more precise control, the "Color Selection" effect, both from the "Alpha Manipulation" section.
Then you can do garbage masking, if needed, with "Rotoscoping" and "Alpha shapes".
You can visualize the selection with "Alpha operations", which can also soften the edges, etc.
In practice, you would probably first make the composite, and then adjust the effects on the second track, to be able to see the final result.
This procedure is probably a bit more complicated to apply, but at least as powerful and versatile as the tool shown in your link.
Some time ago I promised to add an "Alpha control" option to the basic color manipulation filters, which would allow secondary color correction to be done on a single track, but there wasn't much interest, so I went to work on other stuff.
Actually the RGB adjustment tool already has an alpha controlled option, so it can be used to do RGB secondary correction in a single track:
1. generate your selection (alpha)
2. apply RGB adjustment with "Alpha controlled" enabled.
Another filter that can do something similar to secondary color correction is the "Key spill mop up". You can use it to de-saturate a given color.