On the number of colours in Quantum Chromodynamics
  It is commonly believed that ${\pi}^0 \to 2 \gamma$ decay shows that there are three colours in Quantum Chromodynamics (QCD). It is shown here that this is not correct. When correct colour dependent charges of the quarks are considered then it is shown that this decay does not make any statement about the number of colours in QCD. 
A. Abbas