Ferrous sulfate (FeSO₄), also known as green vitriol, undergoes a series of changes when heated, resulting in a change in color. Here's a breakdown:

* Initial Color: Ferrous sulfate is typically pale green when hydrated.

* Heating Stage 1: Upon heating, ferrous sulfate loses its water of crystallization, turning into a white anhydrous form (FeSO₄). This is a dehydration reaction.

* Heating Stage 2: Further heating leads to the decomposition of ferrous sulfate into ferric oxide (Fe₂O₃), sulfur dioxide (SO₂) and sulfur trioxide (SO₃). This process is accompanied by a color change from white to yellowish-brown.

* Final Product: The final product, ferric oxide, is a reddish-brown solid.

Therefore, the color of ferrous sulfate upon heating can be:

* White (anhydrous form)

* Yellowish-brown (during decomposition)

* Reddish-brown (final product, ferric oxide)

The exact color you observe might vary depending on the heating temperature and the specific conditions.