When it comes to printing on Kraft paper, black and dark brown tend to be the most common and most effective colours to use. These colours help to emphasise the natural texture and colour of the stock, while providing a clear and easy-to-read design. Other colours, such as earth tones or muted shades, can also work well on Kraft paper depending on the desired aesthetic.
It's worth noting that photographs don't tend to reproduce well as the brown colouring of the stock can affect the appearance of the image. In fact, the paper colour will alter the appearance of most colours, so it's important to carefully consider your choice of design to ensure it remains visible and effective when printed.
In our experience, simple, clean designs with bold fonts and high contrast colours tend to be most effective.