Why do my frontal sinuses appear slightly darker(shadow) in the mirror?mild pressure+mild congestion, morning eyelid swelling, clear mucus, no fever.

Sinusitis: Sounds like you have sinusitis, try over the counter decongestants and nsaids (like motrin), if it does not clear, see your doctor.

Sinusitis: it is possible that your symptoms could be from a sinus infection, even without a fever. Your symptoms warrant an evaluation, first by your primary care, and then at some point go see your eye doctor.