Can I send a text message when it's dark?

You can't send text messages in this situation.

When a phone number is blacklisted (blacked out), you can't send messages to the other party. This is because most mobile phone systems and communication operators will set up corresponding interception mechanisms to prevent short messages sent by black numbers from reaching the target mobile phone. Although the hacked number can't send SMS directly to the target mobile phone, the other party will receive a notice from the operator or a third-party service, indicating that the hacked number's SMS has been intercepted.