Add the Glowing: option under the Lore: option. Here is an example:
   
 
    
    
     Code (Text):
    
 
    
       RankUp:
     
     Item: '331'
     
     Name: '&8&l>&7&l>&c%Arg% Voucher&7&l<&8&l<'
     
     Lore:
     
       - '&7Use this voucher to rank up to &c%Arg%&7.'
     
       - '&7&l(&6&l!&7&l) &7Right click to redeem.'
     
     Glowing: true
     
     Commands:
     
       - 'pex user %Player% group set %Arg%'