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)(11,12)(13,15)(14,17)(16,18)(19,20)(21,23)(22,24)(27,33)(29,37)(31,35)(32,36)(1,2)(3,5)(4,6)(7,8)(9,11)(10,12)(13,18)(14,22)(15,16)(17,24)(19,23)(20,21)(25,26,30,28)(27,31,33,35)(29,32,37,36)(34,38,39,40)(1,3,4,7)(2,5,6,8)(10,13)(11,16)(17,21)(19,22)(25,27)(26,31)(28,35)(29,34)(30,33)(32,38)(36,40)(37,39)(9,12,15,18)(10,16,13,11)(14,20,23,24)(17,22,21,19)(25,28,30,26)(27,31,33,35)(29,36,37,32)(34,38,39,40)(9,13,15,10)(11,18,16,12)(14,21,23,17)(19,24,22,20)(25,29,30,37)(26,32,28,36)(27,34,33,39)(31,38,35,40)(9,14,15,23)(10,17,13,21)(11,19,16,22)(12,20,18,24)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.