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