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