My dad's first car was, I now realise, rubiginous. It was a second hand (at least) 1965 Vauxhall Viva, and was in fact so rubiginous that when a wing dropped off and the replacement came coated in anti-rust paint, no one ever got round to giving it a top coat because it matched perfectly.
Why the anti-rust paint was exactly the colour of rust I have no idea at all.
Rust is usually a rather horrible colour, I think, though I don't think it deserves the name rubiginous (you say it rooBIDGinnus).
But I suppose the word might be useful if it occurred in a poem - a rubiginous fox, perhaps - because then you'd know straight away it was a rubbish poem and could go off and read a better one.
Sunday Rest: rubiginous. This word comes from the really horrid Latin word rūbīginōsus, from rūbigō, rust, from ruber, red.