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