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