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