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