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