That sounds like a really interesting experiment! Because chlorophylls respond to light at different wavelengths, the red and green lights you use will likely show an effect on plant growth and development.

Both chlorophylls A and B peak in responsiveness around the wavelength of red light, making this light highly effective in promoting growth and flowering of plants, as it can accelerate the rate of photosynthesis. Previous research has shown that because of this, under red light plants grow especially thin and elongated.

Green light, on the other hand, is less effective at promoting photosynthesis as the wavelength of this light does not effectively stimulate chlorophylls. However, green light can penetrate deeper into plant tissue than red light, helping drive photosynthesis in the inner layers of the plant. Despite this, with only green light the plant may not be able to metabolize effectively. All in all, I would hypothesize that the plant under red light will grow at a more accelerated rate than the plant under green light. Hope this helps!