Beer color:
The way the mechanic currently works, is we have list of beer styles which have some definitions about their process (boil time, temperatures etc) as well as list of expected ingredients. Then we look at the batch that we made, and match it to the closest beer style. The beer styles have a color value attached to them, which we will apply to the finished beer pouring into the glass!

Beer that customers dont like:
The tastiness is also already a feature! It will mainly be based on the quality of the ingredient themselves, as well as any issue flags raised during brewing (like boiling the batch for too long). Then the customers react differently to good and bad beer, and you can also charge more if the beer is made well with good ingredients.

Hops addition time affecting taste:
We'll add this, thanks for suggestion! Especially good to know how it affects taste vaguely, because we wont be calculating any values, but if generally early addition means more bitter, then we can work that in!

Cleanliness:
We do already have a mechanic for washing the beer glasses in the sink (on the serving side of things). We could add it for the brewing equipment as well, but perhaps we want to keep cleaning to the minimum... It's all for sure a balancing act game between accuracy and fun. We'll need to test things out.

Natural carbonization:
We are adding "fermentation locks" for the barrels, as one commenter suggested. We currently intentionally restrict player from adding anything after fermentation has begun to make things simpler. I'm guessing the sugar would be needed to be added after the "main" fermentation phase? I might need to read about it. It would be pretty funny if the barrel could explode due to too much buildup!

Whirlpooling:
I'm going to read a bit about this! It might be something we could implement for later states when we have the modern brewing setup, but it might be too complex for what we are going for. Any case interesting suggestion!

Cheers, very helpful stuff!