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