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