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