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