Dexter's lips changing colour

[pa.wilkins]

Hi everyone - I wasn't sure which section to put this in. 

We have a 3 year old male blue roan show cocker, Dexter. Over the last few months we have noticed that his lips are changing from black to pink.  They are now black at one side, pink at the other - I just wondered whether anyone knows whether this is normal or whether it indicates anything?  Thank you for any information

Paula

[dipsydoodlenoodle]

I've noticed Charlie's getting lighter, but I've no idea what it is...he's also 3.