Use the ChooseColorA function in comdlg32.dll.

Compare this technique to the one in Let the user select a color using the CommonDialog control or red, green, and blue sliders.

Public Sub modNumberColor(ColorNumber, BoolCancel) '
    ' colornumber is the color chosen, boolcancel user
    ' pressed the cancel button
    
    On Error Resume Next ' used for when file does not exist
    ReDim CustomColors(0 To 63) As Byte
      
           'first row
           'box1
           CustomColors(0) = 139   'red
           CustomColors(1) = 155   'green
           CustomColors(2) = 184   'blue
           'box2
           CustomColors(4) = 188   'red
           CustomColors(5) = 213   'green
           CustomColors(6) = 254   'blue
           'box3
           CustomColors(8) = 115   'red
           CustomColors(9) = 172   'green
           CustomColors(10) = 183  'blue
           'box4
           CustomColors(12) = 200    'red
           CustomColors(13) = 249   'green
           CustomColors(14) = 198   'blue
           'box5
           CustomColors(16) = 189   'red
           CustomColors(17) = 194   'green
           CustomColors(18) = 253   'blue
           'box6
           CustomColors(20) = 200    'red
           CustomColors(21) = 249   'green
           CustomColors(22) = 255   'blue
           'box7
           CustomColors(24) = 108    'red
           CustomColors(25) = 213   'green
           CustomColors(26) = 210   'blue
           'box8
           CustomColors(28) = 236   'red
           CustomColors(29) = 164   'green
           CustomColors(30) = 236   'blue
           
           'default colors load
           '2nd row
           'box9
           CustomColors(32) = 160   'red
           CustomColors(33) = 160  'green
           CustomColors(34) = 160  'blue
           '10
           CustomColors(36) = 160   'red
           CustomColors(37) = 160  'green
           CustomColors(38) = 160  'blue
           '11
           CustomColors(40) = 160   'red
           CustomColors(41) = 160  'green
           CustomColors(42) = 160  'blue
           '12
           CustomColors(44) = 160   'red
           CustomColors(45) = 160  'green
           CustomColors(46) = 160  'blue
           '13
           CustomColors(48) = 160   'red
           CustomColors(49) = 160  'green
           CustomColors(50) = 160  'blue
           '14
           CustomColors(52) = 160   'red
           CustomColors(53) = 160  'green
           CustomColors(54) = 160  'blue
           '15
           CustomColors(56) = 160   'red
           CustomColors(57) = 160  'green
           CustomColors(58) = 160  'blue
           '16
           CustomColors(60) = 160  'red
           CustomColors(61) = 160  'green
           CustomColors(62) = 160  'blue
       
       'read custom colors out of file and load into custom
       ' color array
       filenum = FreeFile
       Open ((App.Path + "\CustomColors.ini")) For Input As _
           #filenum
       For i = 32 To 62
       Input #filenum, i, CustomColors(i)
       Next i
       Close #filenum
       
       Dim cc As CHOOSECOLOR
       Dim Custcolor(16) As Long
       Dim lReturn As Long
       
       ' Store the initial settings of the Choose Color box.
            
       cc.lStructSize = Len(cc) ' size of the structure

       ' If you comment out the following line,
       ' the dialog appears in the upper left corner
       ' of the screen.
       cc.hwndOwner = Form1.hWnd 'Form1 is opening the
           ' Choose Color box

       cc.hInstance = 0 'not needed
       'cc.rgbResult = frmLogon.BackColor  'doesnt work
       ' 'set default selected color to Form1's background
       ' color
       cc.lpCustColors = StrConv(CustomColors, vbUnicode)
       cc.flags = CC_ANYCOLOR Or CC_RGBINIT 'allow any
           ' color, use rgbResult as default selection
       cc.lCustData = 0  ' not needed
       cc.lpfnHook = 0  ' not needed
       cc.lpTemplateName = ""  ' not needed
       
       'open color dialog box
       lReturn = ChooseColorAPI(cc)
       
       If lReturn <> 0 Then
           ColorNumber = cc.rgbResult
           CustomColors = StrConv(cc.lpCustColors, _
               vbFromUnicode)
           
           'store custom colors in a file
           filenum = FreeFile
           Open ((App.Path + "\CustomColors.ini")) For _
               Output As #filenum
           For i = 32 To 63
           Write #filenum, i, CustomColors(i)
           Next i
           Close #filenum
       Else
           BoolCancel = True
           Exit Sub
       End If
End Sub