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