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