An American socialist moves to the USSR

 Two American socialists want to abandon their capitalist hellhole home and move to the workers' paradise that is the Soviet Union. However, they are suspicious of Soviet propaganda, and are worried that the country is worse than it claims.

So, they come up with a plan: one will go first and live there for a month, then write a letter back. If all is well, he will write a letter in black ink. If things are bad and he has to lie, he will write a letter in blue ink.

The first one moves away, and a month later, he sends a letter written in black ink. He praises everything about the Soviet Union: the economy, the quality of life, the political freedoms, and everything else one could think of.

The last line of the letter is "However, there are some minor trinkets that are hard to find, like a pen with blue ink."