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