Is all makeup forbidden, or is it permissible to use what is not obvious to the eye, such as makeup that is the same color as the natural skin tone?

It is not permissible for a woman to apply cosmetics when leaving her home with her face uncovered, because this is considered adornment that must be concealed from non-mahram men, based on the Almighty's saying: "And not display their adornment except what is apparent thereof." However, if the face is covered, or if there are no non-mahram men present, there is no objection to applying them, provided they are not harmful. And if the cosmetics are not apparent to the observer, even from close up, then there is no harm in them.