A fifth of those in the capital were seen in the funereal color on Friday. Chiluba was accused of diverting nearly $500,000 of state money but was found not guilty in August.
Local organizations asked Zambians to henceforth wear black every Friday and to honk car horns or blast whistles for 10 minutes at 5 p.m. (1500 GMT)
The groups want the government to reverse its decision to not appeal the judgment and for Chiluba's presidential immunity not to be restored.
They are also demanding the justice minister and director of public prosecutions resign over their handling of the case.