a smile is the best makeup a girl can wear identify the error and explain the correction

Solution:

Error: smile is the best makeup a girl can wear
Correct sentence:  Smile is the best makeup a girl could wear

Explanation: 'Can' refers to a general truth or something that has a strong sense of possibility. 'Could' refers to something that has a weak possibility, or something that might happen, but is not necessarily a general truth. Hence, in this particular case "could" will be used instead of can.