Why does Bootstrap define @ brand-primary with darken ()?

Question

In the Bootstrap file, variable.lesssome colors are defined as follows:

@brand-primary:         darken(#428bca, 6.5%); // #337ab7
@brand-success:         #5cb85c;
@brand-info:            #5bc0de;
@brand-warning:         #f0ad4e;
@brand-danger:          #d9534f;

What is the point of using darken()for @brand-primary, why just write directly #337ab7?

Answer 1

The original color was darkened to contrast the accessibility of link colors. This was done at this commit Mark Otto . From the discussion:

@brand-primary , , . ; .