The Latchable lumar button is a button added by RedLogic. It glows in 16 different colors (see below). If the player presses it, it will emit a short redstone signal. The difference between this and the Lumar button is the ability to lock the Latchable lumar buttons into place.
The button can switch between modes when the player shift right-clicks on it with a Screwdriver:
Default: The light turns off when the button is pressed.
Inverted: The light turns on when the button is pressed.