At first glance it might not be very obvious why Follying a Bishop, rather than a Knight, may be useful.
After all, two Bishops of the same coloured square can be a dicey combination. Then again, on the other hand it might be just what you need.
In any case, dual-coloured Bishops are not a foregone result, since there are more Follying options for a Bishop than there are for a Knight, such as when Castling, and herewith the ease to replenish the balance.
This article is not intended as an in-depth Opening study, yet I would like to demonstrate how firstly, Follying is extremely useful as a method to free a Queen or even a King from a Knight shackled against it.
Secondly, this article demonstrates how Follying a Bishop can prove very cunning, particularly whence your opponent is caught offguard, and highlights how dual-coloured Bishops can deliver a very strong blow.