Getting RGB values from an image

Is there any way to find the RGB value of a pixel in an image that has been drawn after setColor has been used to change the drawing color to something other than 255,255,255? I'm attempting to make a Gui module that uses both greyscale images, and generated rectangles, lines and points, in such a way that I can set the color to like OliveGreen (131,193,124) for instance, and have the lines and rectangles generated be the same color as the greyscale graphics. I suspect my solution may lie in dealing with pixMaps some how, but I have no idea how to go about it.

Here's what I have so far, but its not working properly

Function DrawBox(UpperLeftX%,UpperLeftY%,width%,Height%,R%,G%,B%

SetAlpha(.7)
SetColor(r,g,b)
DrawRect(UpperLeftX,UpperLeftY,Width,Height) 'draws a semi-transparent rectangle for the body of the box
SetAlpha(1)
DrawImage(GuiImage,UpperLeftX-16,UpperLeftY-16,13)  'fancy looking corners from images
DrawImage(GuiImage,UpperLeftX+width,UpperLeftY-16,14)
DrawImage(GuiImage,UpperLeftX-16,UpperLeftY+height,15)
DrawImage(GuiImage,UpperLeftX+width,UpperLeftY+height,16)
SetColor(51 + r Mod 255, 51 + g Mod 255,51 + b Mod 255) 'side lines
DrawRect(UpperLeftX,UpperLeftY-3,width,3)      
DrawRect(UpperLeftX,UpperLeftY+height,width,3)
DrawRect(UpperLeftX-3,UpperLeftY,3,Height)
DrawRect(UpperLeftX+width,UpperLeftY,3,Height)
SetColor(108 + r Mod 255,108 +g Mod 255 ,108 +b Mod 255)  'middle stripes
DrawLine(UpperLeftX,UpperLeftY-2,UpperLeftX+width-1,UpperLeftY-2)
DrawLine(UpperLeftX,UpperLeftY+height+1,UpperLeftX+width-1,UpperLeftY+height+1)
DrawLine(UpperLeftX-2,UpperLeftY,UpperLeftX-2,UpperLeftY+Height-1)
DrawLine(UpperLeftX+width+1,UpperLeftY,UpperLeftX+width+1,UpperLeftY+height-1)
SetColor(255,255,255)
endfunction

the colors I'm trying to match are (51,51,51), and (108,108,108) I tried to do it by SetColor(51 + r Mod 255,51 +g Mod 255 ,51 +b Mod 255), and SetColor(108 + r Mod 255,108 +g Mod 255 ,108 +b Mod 255)
but that hasn't been working for me. Any help would be greatly appreciated.

Yep, you have to make it a pixmap, and then use readpixel

how would that work even after the color has been changed from the one in the file by using the SetColor function?

Setcolor doesn't change the pixmap.

Making a pixmap out of an image only changes a few bytes for an address I assume? It's not like the whole pic is copied (as a complete instance) to a pixmap instance? E.g. Can one do fast animations by constant editing of pixmaps of those images?

I did some testing, and I don't think that readpixel is the solution to my problem. I want to be able change the colors displayed when drawing a png with the setColor function (or if I can get a similar effect with pixmaps, and then find the rgb value of the result, ie the rgb values being shown on the screen after a greyscale has been drawn using drawImage after setting setColor to something other than 255,255,255. Perhaps I'm going about this the wrong way though, would it be better if instead I drew my lines and rectangles with a known rgb, and then used write pixel to change values in a pixmap?