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