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