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