Here's one.  I'm sure there are others.

Hi

Overnight Lactic acid bacteria culture were streaked on the surface of plates containing ruthenium red milk (10 % w/v, skim milk powder, 1 % w/v, sucrose and 0.08 g/L ruthenium red, 1.5 % w/v agar). After incubation at 37 °C for 24 h, non-ropy isolates gives red colonies due to the staining of the bacterial cell wall, while ropy strains appeared as white colonies.

Thanks Mister Cote for this articale. And Thanks to you too Anila for protocole wich i looked for.