hgweb: improve colors for comparison page
delete: red -> red
insert: green -> yellow
change: yellow -> gray
Ancestors of 54 2 0 Ancestors of 6 and 53 4 2 1 0 Ancestors of 5 and 44 2 0 Ancestors of 7, stop at 66 Descendants of 57 8 Descendants of 5 and 36 7 8 Descendants of 5 and 45 7 8