Hello! I'm new with Poser, but am slowly figuring it out. I had a question. If, say, I wanted to alter a figure's face and draw, for example, circles around the eyes which would be a different colour than the overall skin, is there a way to achieve this in Poser without resorting to Photoshop (which I don't have)?

Do a search in this forum for Poser mask materials in this forum.  You can mask things out in the material room and change their color.

For anything more complex you'll need a to make some masks in some thing like photo shop.  Gimp is free and Paintshop pro is inexpensive (what I use at home).

select head, open group editor, create new group, name group, select polygons of interest (e.g. the ones in a circular zone around the eye), assign material name. in materials room, assign new colour to said material. otherwise, download an image of a circle somewhere, then apply it as a face tattoo in materials room.