Using two laser pointers of different wavelengths (green and red), we can show that different wavelengths of light produce different two-slit patterns.

Using two lasers mounted in adjustable carriages, a double-high slide holder placed on a stand, two double-slit slides and a white-paper screen, we can produce the two patterns shown here.

Plug in the laser power supply and turn it on. Place the slide holder about 30 cm from the lasers.

Tape a piece of white printer paper to the wall.  The white paper will fluoresce from the blue laser light, making the blue pattern equally bright to the red.

Now carefully adjust the laser mounts to get the beams to illuminate the same slits in each slide and the pattern to show on the screen, centered as below.  It takes some practice to make all the adjustments for the correct distances and angles. Each laser has a left-right linear adjustment, an up-down linear adjustment, a tilt up-down angle adjustment and a left right-angle adjustment.

If the laser mount block is handled gently, little adjustment should be necessary.