Well that's the million dollar question isn't it? To be honest there are probably other forum members better equipped to answer this question than myself (Onyx,Cnaf,Dorsan etc)
However, one consistent belief among experienced members of the community is that the colour of the respective Town Hall(s) is fairly irrelevant.
There's also the post match variables of "did they turn up/use their attacks" and/or "were they rubbish at attacking" to also consider, which is often a contentious issue.
Sometimes we read about forum members complaining about a terrible match, then 24 hours later, we read "We won!". It's then easy to jump on the thread, and post "Well it obviously wasn't a bad match then wasn't it??" - discuss....hmmm!
Personally, I think that a match should be evaluated only at the point when the match is defined, regardless of the subsequent details of the war itself, but I realise others have different opinions here!
So, what is "ok"?
Back to the colour of the TH in particular, I posted the thread below at the end of May, where my own clan experienced a series of wars where we had TH11 deficits, but I deemed the matches fair/ok, at the time based upon actually evaluating the offensive and defensive strengths of both clans, regardless of the colour of the TH.
https://forum.supercell.com/showthre...es-v-Wardens-!
However, I feel many players have wide ranging opinions about what they would deem as "ok", especially (as you quite rightly intimated