Question

What is the significance of yellow colour in to topo

Answer 1

in toposheet yellow colour is for cultivated lands.

Answer 2

Topographic maps may use different colors to represent area features. Most topographic maps will use green for vegetation or national parks and wildlife management areas. They will also use blue for rivers, lakes, or other bodies of water. Red may also be used to represent areas of significant importance and yellow is used for arable lands or agriculural  lands.