Dylan plays it differently constantly throughout the song. I just used the patter from the harmonica solo

    C                                  E        Am
Perhaps it's the color of the sun cut flat I'm  coverin'
    D/F#            
The crossroads I'm standing at
   C/G                        G              Am        
Or maybe it's the weather or something like that
    F              C/G   G   C      G
But mama you been  on    my  mind

             C                                          E           Am
I don't mean trouble please don't put me down or get upset I am not pleading
    D/F#            
Or saying I can't forget you
   C/G                        G               Am        
I do not pace the floor bow down and bent but yet
    F             C/G  G  C      G
But mama you been on   my mind

       C                                                                    
Even though my eyes are hazy and my thoughts they might be narrow where you 
E                 Am
been don't bother me
    D/F#            
Or bring me down with sorrow
C/G                             G             Am        
I don't even mind who you'll be waking with tomorrow
    F              C/G  G  C      G
But mama your just on   my mind

         C                                  E              Am
I'm not asking you to say words like yes or no please understand me
    D/F#            
I have no place I'm calling you to go
          C/G                               G                 Am
I'm just whisperin' to myself so I can't pretend that I don't know
F            C/G   G   C      G
Mama you are on    my   mind

Harmonica Solo

         C                                                       
When you wake up in the morning baby look inside your mirror you 
E               Am
know I won't be next to you
    D/F#            
You know I won't be near
              C/G                      G               Am
I'd just be curious to know if you can see yourself as clear
    F              C/G     G      C      
As someone who has had you on his mind