Section line should be bolder than grids header line

after checking this I would propose some different variant, as IMO this would look very bad.

So couple of other proposals. I think that colorful section lines add too much noise.  My favourite is with section separator made 1 px thicker (2px) and table header line 1 px thinner. WDYT?

Indeed, this does not look very good, I'm leaning towards your proposition, it seems cleaner.