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