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