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