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