Spanish to English Art/Literary Poetry & Literature

I'm translating a Colombian telenovela and this term has come up. I am familiar with "príncipe azul" which is what we in English would call a "prince charming." The character in the telenovela seems to be using it synonymously, but I do not understand why she says "gris" and not "azul." She is a middle-aged woman getting ready to travel to Spain. She says among the lines of "¿Quién sabe? Quizás podría encontrar mi propio príncipe gris por allá" to her daughter.