You can customise the colours of the primary and secondary buttons on your tracking page so that they are different from the black and white defaults.
This is done in the sixth step of the brand wizard:
Once you click Edit to modify a primary or secondary button, the Button style dialog drops down, allowing you to specify the Hex values of the fill colour, outline colour and text colour. You can also specify the rollover style (to be activated when hovering over the button).
After you have entered a valid hex value, the new colour will automatically appear in the button examples, helping you to preview your designs.
Click Finish editing to save your changes, or Reset button to default to abandon them.
Click Next to move to Fonts.