  As a color confinement mechanism, a dual Meissner effect due to Abelian
monopoles involved in QCD has been discussed so far in various ways. But still
there is an important problem unsolved. It is gauge invariance of the schemes
or, in other words, the reason why non-Abelian color confinement is explained
by means of the Abelian dual Meissner effect. Here it is shown that a random
Abelian method based on the violation of non-Abelian Bianchi identity (VNABI)
could prove SU(3) invariance and explain why color-singlets alone can survive
in the confinement phase of QCD in the framework of the Abelian dual Meissner
effect due to Abelian monopole condensation. This is completely different from
the 't Hooft's Abelian projection scheme which introduces an additional partial
gauge-fixing or the idea of Bonati et al. which is based also on VNABI. Bonati
et al. say that VNABI is related to the 't Hooft tensor and the relation can
prove the gauge invariance of the 't Hooft's Abelian projection schemes. But
the last idea is found to be incorrect. Existence of the relation between VNABI
and the 't Hooft tensor alone can not account for gauge invariance of 't
Hooft's Abelian projection schemes.
