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