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