Conditional formatting based on maximum deviation in range

I have a range of cells containing measurements, formatted as fractions to 2 digits: 68 3/16, 67 7/8, 67 3/4, 67 15/16, etc. I am trying to add conditional formatting that will analyze and highlight the range based on 3 scenarios

Green: difference from largest to smallest numbers is between (and including) 0 & 1/4
Yellow: difference from largest to smallest numbers is between 1/4 and 1/2
Red: difference from largest to smallest is greater than 1/2

I have multiple sets of ranges, independent of one another by a blank row right now. Can I add some kind of IF statement for the CF based on if there is a number in the cell above or below to set the range, or how can I apply this to the entire column?

Thanks in advance!