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