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