Yes you can but it may not turn out the color you want, and also it can dry out your hair more and damage it if it isn't conditioned well.
Can You Put Dye On Hair Already Dyed?
If you want to lighten previously colored hair, you will not be able to do that by using another color. Color will not lift color.
If you are going darker, then the roots should be processed for around 15 minutes first, then the color pulled through the previously colored hair for no more than 10 minutes. Same goes for re-touching when using the same color you previously used.
If you apply color on top of previously colored hair and process it for the full amount of time, you will certainly end up with damaged, dried out hair and uneven color results.
If you continue to over process the hair in this manner, you will end up with a lot of breakage.
If you are going darker, then the roots should be processed for around 15 minutes first, then the color pulled through the previously colored hair for no more than 10 minutes. Same goes for re-touching when using the same color you previously used.
If you apply color on top of previously colored hair and process it for the full amount of time, you will certainly end up with damaged, dried out hair and uneven color results.
If you continue to over process the hair in this manner, you will end up with a lot of breakage.
Going to a salon will probably have the best results. But if you do something over and over again it will eventually get there. Bleaching before changing color is good. Also product "color oops". Get a good conditionor, and don't color too often.