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)(14,15)(16,20)(18,19)(21,22)(23,24)(25,26)(27,34)(28,29)(30,33)(31,35)(32,38)(36,37)(39,40) involution — undirected(1,2,5,6)(3,7,4,8)(25,27)(26,32)(28,39)(29,37)(30,36)(31,38)(33,40)(34,35)(10,15)(11,16)(17,22)(18,23)(25,28,31,30)(26,29,35,33)(27,36,38,39)(32,40,34,37)(1,3,5,4)(2,7,6,8)(9,11,14,16)(10,12,15,20)(13,18,21,23)(17,19,22,24)(25,29,31,33)(26,28,35,30)(27,37,38,40)(32,39,34,36)(1,4,5,3)(2,8,6,7)(9,12)(10,16)(11,15)(13,19)(14,20)(17,23)(18,22)(21,24)(25,30,31,28)(26,33,35,29)(27,36,38,39)(32,40,34,37)(9,13,14,21)(10,17,15,22)(11,18,16,23)(12,19,20,24)(25,27)(26,34)(28,36)(29,37)(30,39)(31,38)(32,35)(33,40)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.