In the “Paint” panel, there are 8 palettes (8 radio buttons). On each palette you can have different settings for the brush and the paint mode. Each of the paint tools and the eraser can have their own palette. They remember the one they point to when you switch between the tools.
By default, palette 1 is given to the paint tools (brush, airbrush, pen, bucket fill) and palette 2 is given to the Eraser tool. So, by default when pressing the Eraser tool, palette 2 will be selected, and when choosing one of the paint tools, palette 1 will be selected.
Always when choosing no color (the white box with a red line a cross it) in the Color Picker tool, the paint mode will be set to “Erase”. And when in the “Erase” mode and a color is picked, the mode will be set to “Normal”.
When using the stylus of the tablet (the part you normaly paint with), the last used paint tool will be picked (By default, the brush tool). When using the eraser of the tablet, the Eraser tool will be used.
So if you want to erase with a color, select the Eraser tool, pick a palette and pick a color.