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