Full Spectrum LED is better than Red Blue LEDs.
Is the lettuce leaf plant investing more on vegetative or generative growth? More leaves in relation to flowering stem length indicates that vegetative growth is more profound, whereas less leaves in relation to flowering stem length indicates generative growth.
Even when growing baby leaf lettuce, a full spectrum is your better bet, for faster development and more batches per year, key in Greenhouse short window seasons. Here a Valoya spectrum test proves this.