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