Re-Dye HairQ: I just dyed my hair last night; can I re-dye my hair today again?
A: You can, provided that your hair will withstand the second chemical process. If you are specifically planning to use deposit-only color, you should be pretty safe. However, in color processes that lift the color, you have to be very careful or you risk seriously damaging your hair. If there is any question whatsoever, you need to perform a strand test. Take a lock of hair from an inconspicuous place and mix a small amount of the hair color formula to test it with.
If the test is successful (and doesn't seem to cause any damage to the hair) you can proceed. However, if there is any sign of damage to the hair, you are going to want to hold off until your hair is in proper condition to withstand the process.
How to color hair
How to perform a strand test
Signs of hair damage
How often can I color my hair before I destroy it?