How to change cell color with NPOI
<pre><code>using NPOI.XSSF.UserModel;
using NPOI.XSSF.Model;

using NPOI.HSSF.UserModel;
using NPOI.HSSF.Model;

using NPOI.SS.UserModel;
using NPOI.SS.Util;


(...)

XSSFWorkbook hssfwb;

using (FileStream file = new FileStream(@"D:\VB\XLSX teste com NPOI\XLSX 1\Book1.xlsx", 
     FileMode.Open, FileAccess.Read))
{
    hssfwb = new XSSFWorkbook(file);
    file.Close();
}

ISheet sheet = hssfwb.GetSheetAt(0);
IRow row = sheet.GetRow(0);

ICell cell = row.CreateCell(5);
cell.SetCellValue("test");
cell.CellStyle.FillBackgroundColor = IndexedColors.BrightGreen.Index;
cell.CellStyle.FillPattern = FillPattern.SolidForeground;

using (FileStream file = new FileStream(@"D:\VB\XLSX teste com NPOI\XLSX 1\Book1ee22.xlsx", 
     FileMode.Create, FileAccess.Write))
{
    hssfwb.Write(file);
    file.Close();
}
</code></pre>

<p>Version of NPOI: 2.1.3.1
I have this code and it is changing the color for the hole sheet and not just the cell... What is the proper way to change the fill color of the cell?</p>

<hr>

<p>Here is the working code, based on the answer that is marked as correct below:</p>

<pre><code>XSSFWorkbook hssfwb;
        using (FileStream file = new FileStream(@"D:\Copy D\Tech\VB\XLSX teste com NPOI\XLSX 1\Book1.xlsx", FileMode.Open, FileAccess.Read))
        {
            hssfwb = new XSSFWorkbook(file);
            file.Close();
        }

        ISheet sheet = hssfwb.GetSheetAt(0);
        IRow row = sheet.GetRow(0);


        ICellStyle testeStyle = hssfwb.CreateCellStyle();
        testeStyle.BorderBottom = NPOI.SS.UserModel.BorderStyle.Medium;
        testeStyle.FillForegroundColor = IndexedColors.BrightGreen.Index;
        testeStyle.FillPattern = FillPattern.SolidForeground;


        ICell cell = row.CreateCell(5);
        cell.SetCellValue("testeeerere");
        cell.CellStyle = testeStyle;


        using (FileStream file = new FileStream(@"D:\Copy D\Tech\VB\XLSX teste com NPOI\XLSX 1\Book1ee22.xlsx", FileMode.Create, FileAccess.Write))
        {
            hssfwb.Write(file);
            file.Close();
        }
</code></pre>