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