Yeah, I'm not entirely happy with the cobwebs. Neither 'yellowed' nor 'greying' appear as such in the original. They are simply 'straw-coloured' and 'grey'.

I chose the dynamic participle form for both to indicate an ongoing process of vibrant colour gradually being lost, as the gypsy's passion is snuffed out by the institution.

So the 'greying' is meant to suggest that the cobweb is losing the brightness and beauty it originally had when first creted, and simply becoming tattered and depressing.

Araña could just be rendered as 'lamp', but you need the sense of 'lots of lines arranged together' to match the chessboard of window bars in the last line.