I might need Specsavers again, but it's possible that the lilac tinting to this glass means your pieces are what is described as 'neodymium' - if it is then that part of the glass which is lilac will change colour depending on whether it's viewed in daylight or under strip light (fluorescent tubing).
I think Christine has commented before that Murano production is often neodymium glass - I forget now, but tube lighting might be the grey response, and daylight is lilac - I think.
Is this blown glass? should we call it something else perhaps - 'hot worked'?