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