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