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