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)(25,33)(27,30)(34,36)(37,40)(38,39) involution — undirected(2,6)(7,8)(9,11,14,21)(10,15,19,31)(12,24,25,38)(13,27,28,22)(16,32,34,40)(17,30,18,35)(20,36,37,26)(23,29,33,39)(1,3,5,4)(2,7,6,8)(9,12,13,26,14,25,28,36)(10,16,18,23,19,34,17,33)(11,20,22,24,21,37,27,38)(15,29,30,32,31,39,35,40)(10,17,19,18)(11,21)(15,30,31,35)(16,33,34,23)(20,37)(22,27)(24,38)(29,32,39,40)(1,4,5,3)(2,7,6,8)(12,25)(16,34)(20,37)(23,33)(24,38)(26,36)(29,39)(32,40)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.