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