Button1.MouseEnterを使用すると、マウスがボタンの上に安定するまでボタンの色が変わりませんが、Button1.MouseHover を使用すると、カラー マウスがボタンの上に置かれたときにボタンの色が変わります。
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
'AddHandler Button1.MouseEnter, AddressOf btn1MouseHover
AddHandler Button1.MouseHover, AddressOf btn1MouseHover
AddHandler Button1.MouseLeave, AddressOf btn1MouseLeave
End Sub
Private Sub btn1MouseLeave(ByVal sender As Object, ByVal e As EventArgs)
Button1.UseVisualStyleBackColor = True
End Sub
Private Sub btn1MouseHover(ByVal sender As Object, ByVal e As EventArgs)
Button1.BackColor = Color.Red
End Sub