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