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