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