The government's 21,600 blue-collar workers here probably will be limited to the same maximum 7 percent pay raise as their 300,000 white-collar federal colleagues next month.

Boosts for the blues -- who range from air-conditioning mechanics to carpenters and laborers -- will be announced soon and put into effect Oct. 21. Raises for white collar and military people will take effect in early October.

Pay for the typical blue-collar aide here averages $7.45 an hour, according to Defense Department data. Nationwide, the blue-collar federal average is $6.97 an hour.

Blue-collar pay is supposed to be linked to rates paid for similar jobs in hometown industries. But just as military and white-collar wages are controlled by the White House, blue-collar salaries are subject to limits imposed by Congress. It is working on a 7 percent lid.

Both white and blue-collar federal workers were held to a 5.5 percent raise last year -- although that ceiling did not stop employes from getting longevity raises when they came due. President Carter put the 5.5 percent ceiling on white-collar and military pay. Congress imposed it on blue-collar workers for the fiscal year that ends this month.

Now that President Carter has proposed a 7 percent raise for white-collar civilian federal workers, Congress is expected to do the same thing for their lower-paid blue-collar cousins. If the new, higher, 7 percent ceiling is approved by mid-October, that would be the maximum that blue-collar workers could get.

But if Congress allows the 5.5 percent guidelines to expire this month and does not replace them, blue-collar employes here -- and their nearly half a million counterparts in the rest of the nation -- could get full raises based on average industry increases.