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