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