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