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