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