Welcome to the Wefugees Community and thank you for your question.
The requirements for the "Reiseausweis für Ausländer" (grey passport) are written in the Sections 5-11 of the "Aufenthaltsverordnung". As far as I could see, the law is not listing specific residence permits as being generally exluded to "qualify" for the grey passport. However, there is also no general legal entitlement to receive a respective travel document. Every case and application will be assessed individually and at the end the decision will always be at the discretion of the responsible immigration office (Ausländerbehörde).
The applicant needs to prove that there is absolutely no bearable/resonable way to get a (new) national passport, which is indeed in practice very difficult. From my experience, even people holding an humanitarian residence permit, i.e. coming from a country of conflict, very often struggle to convince the immigration office and subsequently are asked to renew their passports at their embassies.
I never learned about a case in which a person with a EU Blue Card according to Section 18b (2) Aufenthaltsgesetz (German Residence Law) received a grey passport. Nevertheless, I will also link two of our experts here. Dear @mbeon-Christine or @mbeon-Rukundo, am I right on this and is there anything you may want to add?
@Isa49 Please don't hesitate to get back to us with any further questions.
All the best,