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