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