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