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