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