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