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