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