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