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