Most people think that the rainbow-colored flag is all there is to the LGBT movement. However, the reality is that there are also flags for subgroups within the community.
For example, bisexuals have a bi flag that some bring to marches> it has three stripes with the top being pink, the bottom being blue, and the middle being purple. The midsection should be a blend of extremes.
These are symbolic of attraction to the same sex, attraction to the opposite sex, and how these all come together for someone who identifies as bisexual. Who their partners are at the moment does not define their gender.
They do not turn straight when they get into a relationship with the opposite sex. They do not become gay or lesbian if they are involved with the same sex. Many struggles with these concepts even among the community so there is still a long way to go towards universal understanding.