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