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