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