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