One vertex per element, one color per generator, with an edge from x to x·s.
(2,5)(6,8)(9,10,13,11)(12,15,16,14)(17,18)(19,20)(21,22)(23,24)(25,26)(27,34)(28,31)(29,37)(30,33)(32,38)(35,39)(36,40)(12,16)(14,15)(17,18)(19,20)(21,22)(23,24)(25,27,30,28)(26,31,33,34)(29,35,38,36)(32,39,37,40)(10,11)(14,15)(18,22)(19,23)(25,28,30,27)(26,31,33,34)(29,36,38,35)(32,39,37,40)(1,2)(3,6)(4,5)(7,8)(9,11,13,10)(12,15,16,14)(17,19,21,23)(18,20,22,24)(25,29,30,38)(26,32,33,37)(27,35,28,36)(31,39,34,40)(1,3,4,7)(2,6,5,8)(9,12,13,16)(10,14,11,15)(17,20)(18,23)(19,22)(21,24)(25,26)(27,31)(28,34)(29,37)(30,33)(32,38)(35,40)(36,39)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.