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