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