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