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