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