When John saw these little glass jars/bottles on the kitchen bench dribbling blue glue everywhere, his first question was WHY!! (You would think he would be used to strange goings on by now.)
Well, I say why not. If you have some plain glass bottles and you would like blue ones instead, then all you need to do is mix food colouring through some PVA glue, swirl it around inside said bottle and let the excess glue drain away. Leave them for a few days to dry completely.
The glue will dry clear and you are left with two pretty bottles. They are suitable for decoration only and if you wanted to put flowers in them you would need to use glass paint. For a quick, easy and cheap alternative to glass paint, I think this method works well and they look so pretty.