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