Yes it can be for me at times too. When you were on the server and asked me if Silverstone looked dark at this track it was fine for me at the time. See screen shots I took 3 seconds after you asked the question...
I did go online later and it was still fine.
I made a video to see how much the track would go dark when a cloud passed, it was still good.
But then 20 minutes into the session there was an extra thick cloud passed, and this made the track looks like your screen snaps...
I do like the mixed weather setting, with out clouds some tracks can look over saturated with colour and look cartoonish, but yes I agree it can get too dark at times. It even makes the track look wet even though this is dry.
Consider making a post at S397 forums to see if others want to see some better lighting when it's cloudy.
The other screen snaps of Malaysia track I would discard as an example, unfortunately this is another track with the Yellow tint problem that happens online only that I found today.