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