If you don't specify the color they will default to green, but not because of 
anything published by the IPC.

Beyond that, here's the background I have but I can't remember where I got it 
from....

-=-=-=-
Why is Soldermask Green?
The green color of soldermask was chosen after extensive testing by the U.S.
military at the National Materials and Procurement Center in Cedar Bluffs
Virginia in late 1954. According to Colonel Robert Bright, Public Liason
Officer, green was found to provide the maximum contrast to the white 
silkscreen ink under all tested adverse situations while still allowing a clear view 
of the underlying circuitry. Every other color tested failed to provide the 
required contrast under conditions of low / high illumination levels and various 
colored light sources. The quantity of Printed Circuit Boards purchased by the 
Defense Department established a "de facto" standard.
-=-=-=-

Jack
On Wed, 1 Sep 2010 10:35:00 -0700, Temkin, Gregg 
<[log in to unmask]> wrote:

>Is green solder mask the default by any IPC standard or is it default by 
common usage?
>
>In other words, if a drawing does not specify the solder mask color, is there a 
color IPC standards default to, or is it uncontrolled?
>
>Thanks,
>
>Gregg

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