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