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