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