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