Painting the face has several purposes, chief amongst these being beautification (as in cosmetics), transformation (as in today's face painting, also traditional clowns), and preparation for war (from the earliest history of mankind). The use of cosmetics can be traced back to the ancient Assyrians (2000 years BC and more), the Egyptians (Cleopatra being a noted practitioner), and the Romans (the court of Nero particularly requiring make up for both men and women).
Amongst the achievements of the European crusaders was the importing of cosmetics from eastern harems back into their home countries, since when their use has been continuous in the western world - though they have not always been considered respectable! On stage a whole range of materials were employed to paint the face before grease-paint came into use - chalk for a white face (e.g. a ghost), umber to suggest a tanned or weather-beaten face, white lead, gold paint, antimony, kohl, rouge, cochineal, cuttle-fish - and a whole further range of products similarly derived from minerals, plants, animals, and insects.
Women on stage (though not it seems the Elizabethan boy actor, for whom blushing youth seems to have sufficed for the expression of femininity) could "colour their faces with certain oils, liquors, unguents and waters made to that end" (Philip Stubbes 1583 - quoted in "the Oxford Companion to the Theatre").
It's interesting just for a moment to consider the main purposes of stage makeup through the ages. In my theatrical lifetime (my first job, as an ASM in a UK Rep was in 1963) makeup has had three purposes, varying as priorities according to circumstances: firstly to highlight key features of the face for an audience seated too far away to appreciate the subtleties properly, secondly to provide facial modeling when the lighting might be too bright and too frontal and tending to flatten the features, and thirdly the long established purpose of disguise.
Initially stage makeup was all about disguise. It still is to a degree, especially in the lower financed end of this theatrical spectrum. The better financed a production is, the more likely an actor can be hired specifically for a role because he most clearly "is" the character. In the good old days of Rep however one company of actors would play a wide range of characters who often had very little in common with themselves, and that's when makeup as disguise comes into its own.
Looking back to the historical starting point for makeup, the ritual dances of primitive tribes, we can deduce disguise - as animals, as spirits, as devils.
Beautifying the face on stage came later, probably post Elizabethan theatre, and probably with a view to enhancing the beauty of the actress playing the role. This might well have been followed as a practice by changing the skin tone of young men required to portray old men.
The trouble with beautification of the feminine face is that the more of it that was needed, the less able the actress became to express emotion on her face. There are a number of very enthusiastic responses to the occasional actress who left the paint off her face and was, as a result, able to supply mobility of expression to her acting, and with it a more satisfying portrayal of humanity. In any analysis of course, disguise and beautification are both about presenting in public a version of oneself that is not the true image. There are all sorts of reasons for doing this, such as vanity, dramatic necessity, invoking the help of spirits and/or ancestors, or simply escaping the long arm of the law.
In many of these purposes face-painting shares a common bond with the world of masks.