One vertex per element, one color per generator, with an edge from x to x·s.
(1,2,4,6)(3,5,7,8)(9,10,14,17)(11,18,20,15)(12,21,13,16)(19,23,22,24)(27,34)(28,29)(31,39)(32,37)(35,40)(36,38)(1,3)(2,5)(4,7)(6,8)(9,11,14,20)(10,15,17,18)(12,19,13,22)(16,23,21,24)(25,26,30,33)(27,35,36,31)(28,37,29,32)(34,40,38,39)(3,7)(5,8)(25,27,30,36)(26,31,33,35)(28,34,29,38)(32,40,37,39)(9,12,14,13)(10,16,17,21)(11,19,20,22)(15,23,18,24)(25,26)(27,31)(28,37)(29,32)(30,33)(34,39)(35,36)(38,40)(3,7)(5,8)(9,13,14,12)(10,16,17,21)(11,19,20,22)(15,24,18,23)(25,28,30,29)(26,32,33,37)(27,34,36,38)(31,40,35,39)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.