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