Actually now that I think about it, it is a bug. It shouldn't just change the candle green, it should replace the bottom with a stick and put the very small top section as a green candle.
Yes. There are plenty of things they could do rather then the way it currently is being implemented. This suggestion here would be the best solution, what I suggested was probably just the simplest way to get around the current "last action during x time period colors the candle" method they use.
It's not the "last action" that decides the candle color. If the candle closes and the price is higher than when the candle opened it is green. If it closes lower than it opened, red. If the asks fill below the candle open price after a dump, the bot will have to buy all coins up to and beyond the open price for the candle to close green.