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