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