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To make it easier for people to understand, instead of having 2 TWAs coloured red, mark in red all TWAs less than the lower one or greater than the higher one, and have all the others green. Everyone will understand green is good and red is bad.

Just my two bob's worth!

I doubt that that is a good idea.
TWA's indicated are the optimal headings upwind and downwind considering the wind direction. That are thus two concrete values and not a range of values green or red.
If people have problems understanding max VMG and the related TWA, than we should make a learning topic to explain it properly.
just my idea.

Yes, but more than just being the optimum values for upwind and downwind, they are also the values below which (for the small one) and above which (for the high one) sailing becomes inefficient. So they should always be avoided, whether you're sailing along the wind axis or not.