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