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