Although 
llwyd is commonly translated as
                              
grey, it's also traditionally used to
                              refer to some shades of brown. You'll sometimes see 
                              
papur llwyd used to mean 
brown
                                 paper, and 
bara llwyd for
                              
brown bread. However, there are also
                              examples of 
bara llwyd meaning
                              
mouldy bread - bread that has gone grey.
                              You'll always be understood if you use 
llwyd where you would
                              use 
grey in English, and 
brown for English
                              
brown; but knowing about the overlap
                              between these Welsh words can help you make sense of them when you see
                              them.