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