how to do color in excel particular cell?

If you want to set a single excel cell, You can use this solution, first need you to find this cell data and then, set the background color, see below code:

Worksheet sheet = workbook.Worksheets[0];
foreach (CellRange range in sheet.FindAllNumber(1502,true))
{
range.Style.Color = Color.LawnGreen;
}
This method is called find and hilight. you can give it a try.