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