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