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