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