Depends man y'know? If the part facing the sun is a desert the it would be very bright, but it also depends on what the territory is, there is a book called the teeming universe and there is planet in there named borold where the trees are brown-ish and the land facing the sun is an eternal hurricane, so its light is dimmer and it hosts a rainforest, but tbh the plant color would be pretty much the same everywhere for the day part and there would be no plants in the night part, due to not having light photosyntesis would be imposible, but if it had a fraction of light then yeah, it would be dark to absorb as much as much light as possible, so in the end the variables are only the day and night parts but you could be right you know, i too am building a story about a magical tidally locked planet and thought of the same thing, but hey do what you want man, i like your way of thinking :)