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