Bleach lightens your hair but it doesn't add tone, so it will just end up looking brassy. If you have used colourb4 to remove the colour from your hair, buying a hair dye in the shade you want to be is a better idea, it will lighten your hair up to 4 shades, depending on what you get and will also add tone so it will look natural and won't be brassy.
It is also difficult to get bleach on evenly unless you really know what youre doing, so it will probably end up looking patchy, whereas home colours are designed for home use by amateurs, so are much easier to put on.