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