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