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