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