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