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