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