Define the axis characteristics. Blanks are used to suppress tick mark labels at positions -2.5 and 2.5.

axis1 label=none 
    value=("-5" '' "0" '' "5")
    color=red 
     width=3;
  axis2 label=none 
     value=("-5" '' "0" '' "5")
     color=red  
     width=3;