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