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