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