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