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