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