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