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