Hi, I'm new to the forum, and stumbled upon this. Sorry if I sounds like I'm interfering.
My hairdresser is a colour specialist. I go in with wild ideas about what colour, but she often tells me "that won't work". How a colour will end up on your hair depends on several things. First thing is obviously the competence and skill of the person actually colouring it, and the rest is down to several things. Including your own natural hair colour, including if you have any grey hair or natural highlights, or if you have any existing hair dye on. Also, the result can depend on the length of your hair and the overall condition. Naturally, your hair is often darker at the roots, especially in summer, due to the UV rays. How long the dye is left on, and how porous your hair is, and even down to if your hair is wavy straight or curly.
My hair is very porous and quite curly, which means it's naturally dry, so soaks up everything you put on it, including conditioner and hair dye! My hair reacts very differently to someone who has straighter, oilier hair.
I have heard that Vosene can help get colour out of your hair too, however, hair dye technology is changing, and dyes that used to fade quicker, don't fade as quick, but it might be worth a try.
Personally, I would try and find yourself a decent hairdresser that is a colour specialist, and just go in and talk to them. They might not be able to fix it there and then, but a quick fix might not be the answer. Although with browner colours, the chemicals aren't necessarily as strong as blonds, so he or she might be able to sort you out. A decent hairdresser will have a look at your hair, and be honest with you of what might or might not work. You could try highlights (if you don't already have them), so your base is the darker brown, but it has lighter parts in it, so may look "softer". Again, worth consulting a decent hairdresser first.
Remember, your hair probably doesn't look as bad as you think! But when something is radically different to what we want, we often assume it's terrible!
Good luck.