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