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)(11,16,19,21)(12,18,20,24)(13,22,23,14)(25,26,30,33)(27,31,34,38)(28,29,32,37)(35,36,39,40)(1,2)(3,6)(4,7)(5,8)(9,11,15,19)(10,16,17,21)(12,13,20,23)(14,18,22,24)(25,27)(26,31)(28,35)(29,36)(30,34)(32,39)(33,38)(37,40)(1,3,5,4)(2,6,8,7)(10,17)(11,19)(12,20)(14,22)(27,34)(31,38)(35,39)(36,40)(9,12)(10,18)(11,13)(14,21)(15,20)(16,22)(17,24)(19,23)(25,28)(26,29)(27,35)(30,32)(31,36)(33,37)(34,39)(38,40) involution — undirected(9,13)(10,14)(11,20)(12,19)(15,23)(16,18)(17,22)(21,24)(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)(10,13)(11,18)(12,21)(15,22)(16,20)(17,23)(19,24)(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.