Double-slit experiment: overlapping fringes (two wavelengths)

In a setup of Young's double slit-experiment, a beam of light containing a red wavelength, ${\lambda }_1=650\text{nm}$‍, and a violet wavelength, ${\lambda }_2=390\text{nm}$‍, create red and violet fringes on the screen.

The ratio, ${\displaystyle \frac{D}{d}}=8000$‍.