One of the problems with the luck column is that there is no upward bound on "bad" luck, whereas there is a negative bound of 1% (or 0% if it takes exactly one share to find a block) - you can only have a -99% luck factor, but you can have a theoretically infinite + luck factor. So the color visualization is kind of misleading... if anyone has any ideas on how to improve the luck factor display, I'm all ears.
Depends on what exactly you want to achieve with the luck factor display, but one obvious way to have a balanced view is to use percentiles. If the round length is N and the difficulty is D, then exp(-N/D) is the (opposite of the) percentile, which is uniformly distributed from 0% to 100% - higher is better and 50% is in some sense average luck (unlike the current luck factor which is green more often than red). Then you can color-code that, maybe even with a continuous gradation from red to green.