Can we shade the rows with different colors in READ-ONLY GRID based on condition?

No. The only option I see is to simulate a grid using nested card layouts. These support any color you want.

Hi Sadhu, 
If you mean background color, then no. But you could use a rich text field to color the text itself in the read-only grid.
Or else you can create a custom grid field using cards and there you can use background colors.