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