In the very wet Pelikan M200 with a Fine steel nib the 'Deep Dark Green' really is very, very dark, much darker than the sample shown above. Almost black while wet. When dry it is little else but an almost black green, the green really only truly appearing here and there through shading. As with so many other inks, appearance depends on the pen and the paper.
I find "Deep Dark Red' to be a slightly darker Diamine 'Oxblood'. Completely similar in essentials, written with Safari Medium and Fine nibs respectively.
'Deep Dark Brown' and Diamine 'Chocolate Brown' seem much of a sameness, an old 50's Duofold dipped in both of them. Could be a very little less red in 'Deep Dark Drown', looking slightly dustier and thinner, but I won't bet on it. Mostly they look like two different batches of the same ink.