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