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