I found the commentary from St. Thomas on I Timothy 2.
He does not use the word "always". That's added by St. Alphonsus by way of interpretation.
St. Thomas uses the word "dye, color, or paint" (
fucare in Latin).
And he says it's a sin, why, because "men do not wish to be deceived." He says that women are not permitted to be "decorated" (
ornari) except on account of men (
propter viros) and men do not wish to be deceived. So the REASON he gives is because men do not want painted women. It's not some absolute reason such as it being contrary to nature. It's because men don't want to be deceived by a painted woman. He also speaks about social norms as being a guiding principle.
So, as we've already discussed, the nature of "painting" was much different back then than the light application of natural-looking makeup. Secondly, men's attitudes towards makeup have changed. Men in general do not reject the female use of makeup, and so if a woman's husband permits it, or even encourages it, then the rationale for it being "sinful", as given by St. Thomas, goes away.
Later in the
Summa he add the consideration about it being OK to cover up natural defects.
For your reading pleasure:
https://aquinas.cc/236/238/~290This is a great resource, by the way. Has both English and Latin ... and has all the Scriptural commentaries from St. Thomas. If there's one good thing that came out of this thread, it's that it led me to discover this link.