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