Your geranium leaves are turning red mainly because the plant is under some kind of stress. Common causes include:

• Excess sunlight : Too much direct sun can damage the leaves and cause red spots or reddening as a natural protective response.
• Watering issues : Both overwatering and underwatering can cause red leaves. Overwatering can lead to root rot, while underwatering causes drought stress.
• Nutrient deficiencies : Lack of nutrients such as phosphorus, magnesium, or zinc can cause red discoloration on leaves.
• Temperature stress : Exposure to cold or extreme heat can cause leaves to turn red.
• Diseases or pests : Fungal infections or pests like aphids and spider mites can weaken plants and cause red spots on leaves.

Checking for these conditions and adjusting care—like ensuring proper watering, appropriate sunlight, and feeding with the right fertilizers—can help the geranium recover. Red leaves are often a sign that the plant needs attention to these care factors rather than being solely a cosmetic issue.