How Do Eclipses Affect the B-V Index of Identical Binary Stars?

[Fernsanz]

Hello.

Given a binary system with two identical components (in particular de B-V index of both is the same), how would you calculate the B-V index of the system? and, how would it change during eclipses?

I have my own answer, but want to contrast it against yours.

 

[zhermes]

B-V is just (a measure of) the color of the system.
If both have the same color, what will the total color be?
If both have the same color, would it change during occultation?