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