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