What do you mean by "not generate harm to the betting platform"?
I think that means that they will only pay less, so that they can stay in profit and run longer in this business.
You cant have a truly fair game where you want to limit certain rolls so that you don't "harm" the house.
I think he is the owner of this casino so why not? Each casinos has their own limits and limits depends on their budget. If their budget is only small, then the limits are also small but if it was high, then it's also high.
Fair means random chance, not rigged odds in favor of the house.
Here is your choice: make it truly fair with equal odds for all colors (and adjust payouts accordingly) or keep the skewed odds and ditch the "fair game system".
That is another definition of being fair. So far, I don't see any nature of rigged here but I think the OP only had a mistake when developing that game and it pays unfairly on their side. Obviously he will follow your first choice but he may need to hire a developer that can do it properly. You hear that OP? There is nothing really special here.