In a Young's double slits experiment, the source is white light, one of the hole is covered by a red filter and another by a blue filter. In this case:

there shall be no interference fringes

The red filter will absorb all other lights except red light and the blue filter will absorb all other lights except blue light. This gives two different waves of different wavelength and hence different frequency which makes them incoherent in nature.

But we use monochromatic light in YDSE for the formation of fringes on the screen.

Hence, there shall be no interference fringes.