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