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