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)(15,22)(18,27)(21,34,36,33)(23,29)(25,32,39,31)(28,35,38,40)(30,37)(2,5)(3,7)(9,11,13,22,14,23,27,37)(10,15,18,20,19,30,17,29)(12,21,25,35,26,36,39,40)(16,28,32,33,24,38,31,34)(1,3,4,7)(2,6,5,8)(9,12)(10,16)(11,21)(13,25)(14,26)(15,28)(17,31)(18,32)(19,24)(20,33)(22,35)(23,36)(27,39)(29,34)(30,38)(37,40)(2,5)(6,8)(10,17,19,18)(15,29,30,20)(16,31,24,32)(28,34,38,33)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.