Sue, if it is a T-5 tube and a T-5 fixture, it makes absolutely no difference whether the tubes are warm, cool, daylight, or gro-light. T-5 is T-5. You can't use T-5 HO tubes in a standard T-5 fixture though. The HO tubes require an entirely different ballast and it would be dangerous to use HO tubes in a standard T-5 fixture because of possible/probable overheating. The reverse is fine though. You can use standard T-5 tubes in a T-5 HO fixture.
