raster colour

Could somebody please tell me the correct procedure for making part of a raster image green, which you can save and plot with no loss of colour?

i am using the following method but when i close autocad down and reopen the file, the colour parts have been lost. The strange thing is though, is that when i go to file-open, the actual preview image shows the green parts still in the image.

my method

1 - create new colour image

2 - insert tiff file

3 - create new green layer

4 - change the parts of drawing i want green to a REM

5 - put REM on green layer

6 - convert rem back to raster (if i merge the rem the colour goes back to black for some reason)

many thanks for any replies

I am not sure to understand what you say!Can you post like screen shot or dwg?..Depend on my understand..you can reduce two steps.I reduce your steps...

my method

1 - create new colour image

2 - insert tiff file

3 - create new green layer(no need)

4 - select the parts of drawing i want green to a REM and REM

5 - change ..by color for green

6 - convert rem back to raster (if i merge the rem the colour goes back to black for some reason)

P.s..What means "REM" ? When you post forum,pls care to clear as you can.You can do like this any shortcut end of your post(...eg...cmd=command line..).