For the same stamp in the 2003 edition:
a. lebhaft violet ultramarine to dark ultramarine
b. (lebhaft) lilac ultramarine
c. (dark) gray ultramarine
Many catlogs seem to use 'blue' and 'ultramarine' as 'similar'. Not
so, they are wuite different. Here an effort has been made to make
them propery I's as 'ultramarines'.

'lebhaft' = 'lively', whatever that means.
'Bright'

publisher. (Scott does not make a color guide and is not consistent in
color names within its catalog. I have found both a non-Scott American
color guide and a Gibbons color guide to be somewhat useful with Scott's
catalog, but only somewhat.)
SG's Colour Guide is so far off the 'historical colours' it's a laugh.
Many of the listed shades aren't even in the 'guide'!

Does your color guide have 'violet blue'? 'lilac ultramarine'? both?,
neither? If only the first, I would strongly suspect that lilac
ultramarine is a new name for violet blue and that you just need to
develop a translation table.
No, they are quite different shades! There is a 'violet blue' and also
a 'violet ultramarine'!

Printing can be differentiated upon such small differences.

As an example, the 2.5d of KE VII in GB. De La Rue printed in
Ultramarine [shades] and Harrison used a Blue [shades]. Very close -
but side by side you can see the difference.

Even without fading and other post-production color changes, colors are
a difficult subject. Inks were once hand mixed so the colors of multiple
mixings tended to vary continuously. Some of the rarest colors may have
been errors that appeared on only one issue, and hence not appear in a
color guide.
Very true, specialists can assign printings to year[s] or events with
the shade. Again, from GB, three shades determine whether pre,
immediately post or rebuilt, the famous Perkins Bacon Fire.