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