Darkening a too blonde base can be tricky. You may want to just go down a few shades, but without the professional touch of a hair stylist, could end up with a brown shade. It is best to always gradually darken your hair to get it to the level that you want. You can do this with hair dye, or with natural remedies at home if you want to stay away from chemicals.
Find a slightly darker shade than the colour you have now if your base has already been coloured. You may want to consult with a professional hair stylist to find a colour that will work for your individual situation. Hair that has already been coloured or bleached to a lighter colour is damaged and will quickly absorb colour, so do not go too dark.
Dye your hair according to the directions for the particular product you have purchased. However, you may want to lessen the amount of time that the dye is on your hair. Again, your hair will be very receiving to colour after recently being dyed, so be careful as to how long you leave the colour on.
Rinse your hair and style as normal. If you did not achieve the colour you wanted, then wait at least one week before repeating the process. By not giving your hair enough time to recover, it will become dry, brittle and damaged.
Brew strong black tea or black coffee. Coffee, black tea and even cocoa can be used as a rinse to darken hair.
Allow the brew to cool off, then apply the brew to clean, wet hair. Let the brew sit on your hair about 5 to ten minutes.
Wash your hair and condition it, then style as normal. This is not a permanent fix, and will need to be redone once a month to maintain the darkened look. However, it does help you avoid re-colouring your hair, which can cause damage to the cuticles and create dry, brittle hair with split ends.
To avoid going too light next time, gradually work your way up to the blonde colour you'd like to achieve. Often times, some people go up four to five shades to achieve a colour, and quickly find out the colour is too light. It is better to lighten your hair over a period of two to three months and find that perfect shade rather than doing it all at once.
Try to keep your hair out of the sun as much as possible when your colour is too light. The sun naturally lightens hair even moreso, which will only worsen your problem.