Generally, if you use a semi-permanent colour, the development time is no more than 20 minutes. If it is left on longer, it goes progressively darker and is actually more difficult to remove than a permanent colour, as the molecules can actually stain your hair’s cuticle scales.
If you are doing it at home, it probably took you about 20 minutes to apply. Add to that the 20 minutes you had to leave it to process, and you can see that some parts of your hair may have had the colour on for 20 minutes longer that needed!
My first suggestion would be to pop into a salon that specialises in colour, for a consultation about your problem. Most salons offer free consultations. You could purchase a professional deep cleansing shampoo to use at home but you would also need to get a professional conditioner to hydrate as the cleansing shampoo can make the hair feel quite dry.
The other option is to chat to your stylist about the option of colour removal. There are great products in the professional market in various strengths that will remove colour without damaging the hair.
Unfortunately, once you have coloured your hair, you lose your own natural blue pigment forever, and you will always be left with a warmer undertone when removing colour. That can be corrected in a salon with a corrective colouring technique where a stylist will use cooler colours to neutralise the warm tones.
Try Redken Hair Cleansing Cream Shampoo, Matrix Alternate Action Shampoo or L’Oréal Anti Residue Shampoo and Redken All Soft Conditioner; or L’Oréal Intense Repair Conditioner.