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