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