Eyeglasses option (4)
I believe the answer is:
tint
'eyeglasses option' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for tint that I've seen before include "'Shade, tone (4)'" , "Quality of colour" , "Hue, shade" , "Shade; colour slightly" , "(Softer variety of) colour" .)