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