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