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