Sending a Happy Ramadan greeting message at work can be a kind gesture, but it is important to consider the workplace culture and individual beliefs of coworkers before doing so.
In a diverse and inclusive workplace, acknowledging and celebrating different religious observances can promote understanding and respect. However, if you are unsure if a coworker observes Ramadan or if they would be comfortable receiving a greeting message, it is best to err on the side of caution and refrain from sending one. It is always important to be respectful and mindful of individual differences in the workplace.