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