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