Color conversion gone wrong?

ok this is the deal.. i have a code to convert an image to a certain color. what i do is get the R G B values and then add a certain value to them. (like 120 to r to create a more red image)

but this code only works correctly with grayscale images what am i doing wrong?

VB Code:

Option Explicit
Dim temp As Long
Dim red As Integer
Dim green As Integer
Dim blue As Integer
Dim color(2) As Integer
 
Private Sub Command1_Click()
Dim x As Long
Dim y As Long
Dim temphex As String
red = rvalue: green = gvalue: blue = bvalue
For y = 0 To Picture1.Width - 1
    For x = 0 To Picture1.Width - 1
      obtainRGB (Picture1.Point(x, y))
      Picture1.PSet (x, y), RGB(color(0), color(1), color(2))
      DoEvents
    Next x
Next y
End Sub
 
 
Private Sub obtainRGB(cValue)
color(0) = Int(cValue / 65536) + Int(red)
cValue = cValue Mod 65536
color(1) = Int(cValue / 256) + Int(green)
cValue = cValue Mod 256
color(2) = cValue + Int(blue)
If color(0) < 0 Then color(0) = 0
If color(1) < 0 Then color(1) = 0
If color(2) < 0 Then color(2) = 0
End Sub