Who can clear this one up re discharge lamps

[PeterG]

When I was a kid, we had a load of floodlights in my local swimming pool. Very unusual - they were twin lamp and the floods themselves were massive with remote gear boxes. On the left hand lamp holder was a SON-T clear tube, and on the right hand lamp holder was another clear tubular lamp - looked exactly like a SON tube in terms of tubular and clear except this one produced light that was a lovely cool white with a blue-ish tint to it. Possibly 250 or 400w sort of size. I think the idea was that they could alter the colour temp of the room.

Anyone have any suggestions what those clear, tubular silver-blue output colour lamps might have been? - we're talking 1980's-1990's era so not too long ago. I'd be interested to know what they might have been running. Any thoughts appreciated. I assumed all mbfu lamps were elliptical and white/Phosphor coated but these definitely were clear tubes yet kicked out a silver-blue-ish light like mbfu.