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