I have a few early C19 wills on vellum - they make for amusing C21 reading, provided you can read the slightly faded copperplate. There's one dated 1827 where the male deceased leaves to his wife 'a chest and wearing apparel and ONE COW' - he also states that he gives his main land to his wife 'provided she shall remain unmarried for the rest of her life'. This may have been a perceived safeguard to make sure his property and money were guaranteed to pass to his children - had she remarried there's always the chance an unscrupulous suitor might have hived it off at some point.
Hope Ivo won't object if I add a little to his last words ............. the colourant is the chemical used to create the colour - probably iron/ferrous oxide for green, although chromium later on ........... and smalt for blue ......... and as far as I know the descriptions 'Bristol green' or 'Bristol blue' gained common usage because some of these colourants - smalt in particular - were imported from the Continent into the port of Bristol - hence the use of the word Bristol.
The colour variation in these glasses, the green ones in particular (some tend towards blue), was due to the obvious inexact control when adding colourant to the batch.