Using Clipping Masks to achieve two-tone text. Note:
A Clipping Mask is simply grouping layers. The clipped layer is
only visible where it intersects the base layer.
In this tutorial we’ll learn to use the Layers Palette
and Clipping Masks.
1. Open a new document, at least 200 dpi for good printing. Create
a new layer and fill half of it with a black rectangle (use the
Shape tool on Fill option, or use the Marquee tool and Flood Fill
with the paint bucket).

2. Ctrl-Click on the layer 1 thumbnail (black rectangle layer)
or right click>Select Layer Transparency to make a selection
exactly the shape of the rectangle.

3. Make another new layer, and fill the selection with white.
4. Use the text tool to type, color black. If the text layer
is not underneath the white layer, drag the layer thumbnail below
white layer.
5. With the white layer selected, go to Layer>Create Clipping
Mask, or Ctrl-G, or Alt-click on the line between the white layer
and the text layer to group them.
You can now reposition the text, change the font or size without
affecting the coloring.