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