I can't think of code to make a form gradually become transparent but here's some code that you can use to change colors gradually. For this to work the ShowModal property of the form has to be set to False. I put the code in the form Initialize event but I assume you'll want to put it elsewhere. Also, many variations of the color are possible.
Dim i As Integer, v As Double
Me.Show
For i = 1 To 200 Step 2
v = 0
Me.BackColor = RGB(i, 50, i)
Do
v = v + 1
Loop Until v = 1000000
DoEvents
Next i