That Caithness design was a limited edition, so if yours is it would be marked Caithness and numbered. The Colin Terris design looks to be three large bubbles over a bed of bubbles, not a coloured layer. I think I'm right in saying that all Caithness is marked, even seconds (CIIG).
The clincher of yours is the base. It isn't shiny and polished is it? A matte base is often an indicator of Chinese glass.