In LLPSI Ch XI, line 12, page 77 there is the sentence:
Lingua et labra rubra sunt ut rosae.
What case and gender is 'rubra' here? It is describing Lingua (nominativus feminina singularis) and Labra (nominativus neutrum pluralis). So which is it? What if one were writing 'Os et lingua huis viri rubra (?) sunt ut rosae' ? What form of ruber, rubra, rubrum would you use?