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