How Can I make the bottom of my object texture a different colour?

[Hazeissad]

I want to have a slight brown tinge at the bottom of this barrel. How can I do this?

[AntonMikhet]

You can will add some decal

[ClockworkOcean]

Decal is correct. You can also use pixel depth offset:

Object Blending with Dither Fade, Pixel Depth Offset and Distance Fields