for the first 4 row it is working from row 4 to 7 set color

Question

for the first 4 row it is working from row 4 to 7 set different fore and back color in data grid view

 for the first  4 rows  it is working fore and Back color.

Then for another 4 rows[4 to 7 rows] i want to set different fore color and back color.

Code as follows;
      

For the First  4 rows code as follows;

           int irows = 0;

           for (int i = 0; i<; datagridView.RowCount; i++)
           {
               datagridView.Rows[irows].DefaultCellStyle.ForeColor = Color.Purple;
               datagridView.Rows[irows].DefaultCellStyle.BackColor = Color.RosyBrown;
               irows = irows + 1;
           }


for the another 4 rows code as follows [row no 4 to 7]

    
      int irows1 = 4;

      for(int i =4;  i<7; i++)
       {
          datagridView.Rows[irows1].DefaultCellStyle.ForeColor = Color.Blue;
          datagridView.Rows[irows1].DefaultCellStyle.BackColor = Color.Aqua;
          irows = irows + 1;
       }

i tried the above code for another 4 rows [row 4 to 7];

but only for the 4 th row color changing but not for the  remaining rows 5  to 7.it is not changing.please help  me.

from my above code,what is the mistake please rectify.i tried but is not working.