Изменение цвета строки в DataGridView

    Dim Cell As DataGridViewCell
    'Закрашиваем последнюю строку в желтый цвет
    For Each Cell In DataGridView1.Rows(DataGridView1.RowCount-1).Cells
        Cell.Style.BackColor = Color.Yellow
    Next

Public Class Form1
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Column1 = New System.Windows.Forms.DataGridViewTextBoxColumn()
        Column2 = New System.Windows.Forms.DataGridViewTextBoxColumn()
        Column3 = New System.Windows.Forms.DataGridViewTextBoxColumn()
        Column4 = New System.Windows.Forms.DataGridViewTextBoxColumn()
        Column5 = New System.Windows.Forms.DataGridViewTextBoxColumn()
        Column6 = New System.Windows.Forms.DataGridViewTextBoxColumn()
        dgv.Columns.AddRange(New System.Windows.Forms.DataGridViewColumn() {Me.Column1, Me.Column2, Me.Column3, Me.Column4, Me.Column5, Me.Column6})
        dgv.RowCount = 6
        For i As Integer = 0 To 5
            For j As Integer = 0 To 5
                dgv(j, i).Value = 12345
            Next
        Next
    End Sub
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        'Закрашиваем столбец 2 в светло-голубой цвет
        Dim st As New DataGridViewCellStyle
        st.BackColor = Color.LightBlue
 
        dgv.Rows(0).Cells(1).Style = st
        dgv.Rows(1).Cells(1).Style = st
        dgv.Rows(2).Cells(1).Style = st
        dgv.Rows(3).Cells(1).Style = st
        dgv.Rows(4).Cells(1).Style = st
        dgv.Rows(5).Cells(1).Style = st
    End Sub
    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        Dim Cell As DataGridViewCell
        'Закрашиваем строку 4 в желтый цвет
        For Each Cell In dgv.Rows(3).Cells
            Cell.Style.BackColor = Color.Yellow
        Next
    End Sub
End Class

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        DataGridView1.DefaultCellStyle.SelectionBackColor = Color.White
    End Sub