How soon can I apply a different hair colour if I' m unhappy with the results of the first application?

My daughter coloured my hair yesterday and it didn't turn out quite as expected. If I'd like to apply a darker colour, how soon can I do it, and will it be affected by the first colour?

What is a VPN?

VPN is (Virtual Private Network) were first used by companies to enable their employees to securely access internal systems such as email remotely (e.g. from home or while on business trips). Today they are increasingly being used for personal use by individuals to protect their privacy while online in public places (e.g. when using the wi-fi connection in a cafe) or in a country where the internet is censored / blocked (e.g. China, Saudi Arabia…).