New Layer Defaults
This section of the palette contains two large overlapping squares - the one in front is the Foreground Color, the one in back is the Background Color. When you are creating a layer of only one color, the foreground color is always used. When you create a region and an outline simultaneously, the region is given the background color. The current gradient fill defaults to dynamically between these two colors. Clicking either will bring up the Colors Dialog to select a new color.
In addition to these two controls, there are two smaller controls located in the corners between them.
The arrows on the upper-right side swap the foreground and background colors.
The letter R on the lower left reverts the foreground and background colors to their default of black on white.
Default Blend Method
Sets the Amount Parameter for new layers. Defaults to 1.00 (Completely opaque)
Used by the bline tool when creating a new Curve Gradient layer. Also used by all Gradient layers as their fill. This defaults to a gradient between the foreground color and background color. Clicking this will bring up the Gradient Editor Dialog