Why Are Tax Forms Blue?

Ever wonder why tax forms are blue? Me neither. But apparently form color is important to the Treasury Department's Inspector General (TIGTA), the branch of the Treasury department whose job it is to worry about such things:

TIGTA also recommended that the IRS seek congressional approval to use additional colors on tax returns and instructions to highlight important warnings and information. Congressional approval would be needed because the IRS used multiple colors on the cover of of its 1995 tax packet and received some negative publicity. After that happened, Congress mandated in the Treasury Department Appropriations Act of 1997 that the IRS could use only two ink colors on tax packages. ...