Colour compensating glass filters are available to adjust a specific colour that your image may have too much of. These colour compensating filters effectively act as light sponges, absorbing excess amounts of a specific colour in different densities according to which filter is selected. By selecting these different densities, very fine adjustments in colour temperature can be made.
Colour compensating glass filters come in red, green, blue, magenta, cyan and yellow.
For technical information, please see this guide to exposure increases required for each density