Usually, no. CTO and CTB gels change color temperature by absorbing parts of the spectrum; they do not add missing wavelengths. If a light has low CRI because its spectrum has gaps or poor overall balance, a gel won’t fix that.

In theory, a filter could slightly improve rendering only if the low CRI is caused mainly by one overly strong narrow band of light and the filter happens to reduce that excess. But that would also reduce output, and standard CTO/CTB gels are not designed as CRI-correction filters.

So while CTO/CTB can shift a light warmer or cooler to match other sources, they generally will not meaningfully improve CRI. If color rendering matters, the practical solution is a better-quality light source rather than trying to correct a poor one with gels.