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