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