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