>How can I design an application so that the colours that I used will look the same on my client's machine as they are doing on mine?
>
>For example on my machine green is really green. On my client's machine green is leaning toward black.
>

THis is a result of the client machine attempting (unsuccessfully) to emulate a color that it can't produce.

When I have to choose colors for a downward compatible system, I set my system's colors to their number (256 or so), so I am seeing what they will see.