Following on from the accidental success of the blue glass bottle bottom on a green neck, I carried on with switching bodies and necks over. Though it’s a matter of personal taste, I think mixing the colours can make them even more effective, no matter what the size or shape.
As coloured glass is more effective than clear for tealights, adding a pleasing tint to the flickering flame and the light radiated, I put a shorter green beer bottle bottom on a clear stubby neck. For a design that would perhaps be to show things off better .eg. for a cut flower vase, a decorative or carved candle , potpourri, coloured beads etc , I put a tall clear body, on a longer green neck.