The orange status LED flashes at a steady rate indicating the board has power.
The green status LED is the bus traffic LED, it will flash any time the 485 bus polls the device. This is a variable flashing LED, although it is normally difficult to notice the difference in the cadence. The polling rate is 115,000 baud which results in a fast blink.
These LEDs provide basic feedback. If the orange LED is out, there is no power to the unit. If the green LED is flashing slow, it is not talking to the control.