Cationic Dyes are those dyes which are parted and give colored positively charged ions, when they are mixed in aqueous solution.

• Having intensive bonding capability.
• Molecular structure is in planar form.
• Positively charged surface groups are stronger over the negatively charged surface groups.

In the Color Index scheme, cationic direct dyes are classified along with Basic Dyes.
In a Direct dye molecule, the chain of conjugation almost always contains two or more aromatic groups.

The word "Direct" implies that the dye has an adequate molecular size so that it has a strong preference to remain on surfaces. In other words, the user can add it "directly," without a fixative or mordant, as it will remain sticked to the surface. Cationic Direct dyes have particularly high affinity for anionic surfaces due to presence of cationic amine groups.

• Cationic direct dyes can be very valuable where (a) the effluent water has to be colorless, or (b) where a high frequency of production changes between different colored products that provides an incentive for keeping the white water free of residual dye.
  
  
• Cationic direct dyes tend to irreversible stain i.e. the first surfaces with which they come into contact. The speckled appearance of paper products is due to this fact. Users may use adequate dilution and add the dye at a point of good agitation if they want to avoid it.