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