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