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