Question

why colour of soil differs​

Answer 1

the colour of the soil differs from place to place because the composition of soil differs from place to place

Answer 2

Soil in this context of Colour means very tiny particles of rock, along with other visible and in visible particles of biological materials, Minerals, Metals, Ash and dyes in the form of clay which would have been carried by stream/water flows, geological events like volcano eruptions, High tides, etc, may be recent or Millions of years back.

Many patches with different colors seen on the land (especially barren beaches/ deserts, are formed because of sudden spurt of different colored soil coming up from underground. The color seen on the surface of land need not be same after a few feet,as the upper layer of sand would have reached there by waves, in a tsunami!

Undersea eruptions carry ash even places/beaches. miles away by under currents in the seas. The clay consisting of say Red oxide/iron Oxide mineral may travel hundreds of Kilometers by rivers making the banks red. So also the Black sand which may contain many Rare minerals which are in black color. White color is due presence if Calcium, china clay/Chalk used in pottery or Zinc oxide !
Yellow or brown comes from Sulfur contents. Ironically some colors may be just for appearance but not real as the real sand if washed may be showing another color and it is due to some plant growth on the surface of tiny rock particles, like tiny moss which makes the sand as Pink or Green...
There are other colors too which are very rare...