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