Grouping Data by 3 Values

Hello All,

I have around 13000 colour measurements in L, a, and b colour space. We are trying to group them by similar colour which involves sorting the three columns as a set rather than independently. I've had some success with lists but this only does one colour at a time and involves manually setting tolerances.

I've attached an example of the data and the most simple result that would do the job, but even better than this would be a way of actually finding and grouping similar colours (say plus or minus 2 units on each value).