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)(11,18)(12,16)(13,22)(14,17)(15,21)(19,24)(20,23)(29,37)(32,39)(35,38)(36,40) involution — undirected(9,11)(10,15)(12,19)(13,20)(14,21)(16,23)(17,18)(22,24)(25,26)(27,34)(28,31)(29,35)(30,33)(32,36)(37,38)(39,40) involution — undirected(2,5)(6,8)(9,12,14,13)(10,16,17,22)(11,19,21,20)(15,23,18,24)(25,27,34,26,30,31,28,33)(29,35,40,32,37,38,36,39)(9,13,14,12)(10,16,17,22)(11,20,21,19)(15,23,18,24)(25,28,30,34)(26,31,33,27)(29,36,37,40)(32,38,39,35)(1,3,4,7)(2,6,5,8)(11,21)(15,18)(19,20)(23,24)(25,29,28,36,30,37,34,40)(26,32,27,35,33,39,31,38)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.