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