Light is an example of something that travels in waves
Light waves come in many different varieties, and can be seen as many different colors. What is the main difference between a light
wave that produces the color blue and a light wave that produces the color red?

The difference in wavelength of light causes a light wave to produce blue color and another light wave to produce red color.

Explanation:

Light is considered to be a part of electromagnetic spectrum. Light experiences variation in wavelength which causes it to have different colors.

A light with blue color has the shortest wavelength while a light with red color has longest wavelength.

Human eyes can not see all wavelengths of light. Visible light wavelength is the only kind which we can detect.

Changing a wavelength will result in change in color of that light ray.

Color of an object depends on the the light that it reflects.

Visible light can be a small part of the electromagnetic spectrum but other ranges of wavelengths also occur. Such patterns are known as colors. Red light is on one side of the spectrum, with the longest wavelength. The shortest wavelength is of blue or violet color. White light is a blend of all colors in the spectrum. Wavelength  interval of red light is ~ 700–635 nm while blue light range ~ 490–450 nm and is considered main difference between such light waves.