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