Speaking of the blue-green alliance, a coalition of labor and environmental groups, plus the trucking industry, filed suit yesterday to prevent the U.S. government from allowing some 30,000 Mexican trucks onto American roads. On Friday, the Bush administration is scheduled to sign regulations that would allow Mexican trucks to cross the border for the first time in 20 years. The coalition contends that doing so would increase air pollution from diesel fumes and violate the Clean Air Act, which prevents the federal government from taking any action that would increase air pollution in regions that do not meet air-quality standards, such as Southern California and other border areas. And truckers have another concern on their minds: Currently, products coming in from Mexico must be unloaded at the border and transferred to U.S. trucks. The Teamsters fear that allowing Mexican truck drivers to enter would cost U.S. jobs and depress wages.