Roborat: here's a list that ive copied from one of my proline/jaco cardboard tags ...

yellow = soft (20) = high wear/very good traction
green = medium (25) = high wear/very good traction
blue rears = firm (30) = moderate wear/good traction
blue fronts = very firm (40+) = low wear/good traction
blue/orange = med-firm (30-40) = moderate wear/poor traction
aqua = medium-firm (27) = moderate wear/very good traction
white = medium-soft (25) = moderate wear/excellent traction
grey = medium (30+) = moderate wear/excellent traction
pink = soft (25) = excellent wear/excellent traction
purple = medium (40) = excellet wear/very good traction
red = firm (40+) = excellent wear/moderate traction
silver = soft (20) = very good wear/very good traction
gold = medium (25) = very good wear/very good traction

for carpet/asphalt application = yellow, green, blue rears, blue fronts
for carpet application = blue/orange, white, grey
for asphalt special application = aqua
for asphalt application = pink
for asphalt/carpet application = purple, red
for dusty asphalt application = silver, gold