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