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