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