What should I do?

What colour do you want ultimately?
If you put colour remover or bleach on the purple it is likely to turn green. This isn't a major issue if your intention is to dye it purple again, but much harder to get out of you are aiming for blonde.
If you fade the purple first, you will have an easier time evening up the base. I would go for dandruff shampoo worked in to just damp hair. Cover and heat with a hair dryer, leave for half an hour to an hour wrapped in a towel, then rinse with hot water. Then deep condition. It is drying, but gives the most colour lift for the damage IMO

I will be re-dying purple and turquoise so I can't imagine it being green will make a difference.

Should I do dandruff shampoo instead of ColourB4?

Ultimately I would like the colour bright, because my hair is a medium to dark brown I know I will need to re-bleach. I'm not sure if I should bleach bath to even out the previously bad bleach job, or what?

What kind of deep conditioning would you recommend? Even if it's just coconut oil, or something like that?

I could take a picture of my hair so you could see what it's like now, if that will help?

I could take a picture of my hair so you could see what it's like now, if that will help?

That would help a lot 🙂

A pic would be great, if you can fade the colour with dandruff shampoo first, a colour remover will be more effective. I try and avoid chemicals as much as possible, so only use the dandruff shampoo method to fade. Like you I would rather take a little more time and preserve the integrity of my hair

I tried to get as much natural light as possible, sorry for the less then perfect quality. I think you can at least make out what my hair looks like.

I must be uglier than I thought. I've scared you both away!  ;D

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How light was it after bleaching? the lengths and ends look brown in the pic, is that orange hair toned to brown with purple dye?
What purple did you use?
Was the hair virgin when you bleached it?

It was lighter in some places than other. I guess it was a sort of Light brown to a coppery blonde. There were some just light blonde highlights as well, for example those fading near my face. The ends are actually a greeny/blue brown colour.

My hair was virgin and a natural dark brown, the color of my eyebrows. The length of it is like a brown with purple on top. I'm pretty sure it was Manic Panic Purple Haze.

OK, well that is good, Purple Haze is pink based so shouldn't go green when bleached.
This isn't going to be easy, but this is what I would do.
First get as much purple out as possible with head and shoulders as described above.
Then you are going to have to go through section by section and correct each strand. Don't try and do your whole head, it is too much hair.
So start at the underlayer. Do a strand test to determine how long you will need to bleach the ends/lengths so that they match the lightest part. Also how long your regrowth will take.
Then apply the bleach bath mix to the regrowth first excluding the roots/first 2cm, then apply to the ends/lengths after the time determined by your strand tests, stopping when you get to the lightest part which is the colour you are aiming for . Apply to the root area last.
If you are accurate with the timing everything should be the same colour at the same point and you can rinse and then repeat  on the next section.
Remember that the lower volume peroxide the slower it works, giving you more time to apply accurately. Make sure every strand is fully saturated and cover the lengths loosely with cling film or a plastic bag to keep moist whilst processing.
Use a really good bleach powder, you will get more lift at a lower volume, so minimising damage.

So I did the anti-dandruff shampoo thing, except I don't have a hair dryer so instead, wrapped my head and sat in a hot bath for 30 minutes. Before I rinsed my hair and I added more shampoo and rubbed it all over my hair. I saw a small amount of purple come out and my husband remarked that my hair does look lighter and a bit less purple this morning. However, there is still some purple that is quite bright and my hair is still dark.

I was thinking I should try the Colour B4 now. Do you think it will be okay? My hair is in really good condition still, other than being a bit frizzier than normal. It doesn't feel dry or horrible.

Also I was planning on cutting my hair only a couple inches or so, should I do it before or after? whenever I've had my hair done in a salon they always do it after the dye my hair and I wasn't sure if there was a reason.

Thank you so much for all your help.

I would cut it first, then you have less hair to handle and will need less product.
Try the Colour B4 on a strand, keep it covered and warm and leave in for the full hour. That way if it doesn't do much you haven't risked your whole head.

I tried a beach bath and although it lightened my hair slightly, it didn't do as much as I would want and I left it for the full processing time. Also, it seems to have turned my hair green as well. When do you think I'll be able to bleach again, in a month?

I have included pictures to see what you think. I tried to do a variety of angles and flash/no flash. If needs be I'll take some pictures in natural light tomorrow, if there is any natural light that is.

The green is from the left over purple.
You won't be able to just bleach bath all your hair and get it even, there are no shortcuts when you are trying to even out and correct a patchy bleach job.
You either have to do the colour correction i described above or get it done at a salon.

Okay. I guess I misunderstood when I read your previous post. I thought you were saying that I could beach bath, but just had to do it in sections because of how much hair I have. I did do a bleach bath in sections, but I guess you meant a little more sectioned then I thought you did.

I suppose I can try it again, I'm not sure if I'll be able to do it right, I'm not a neat person. Only the very top bit of my hair has highlights if I just pin that bit up and do the underneath all in one go, but obviously doing the darker bits first and moving up to the lightest bits and then focus just on the top, that might be easier.

How long would you recommend I wait before I try bleaching again? I do appreciate your help and I'm not trying to go against your advice. I'm sorry if it seems like I'm just ignoring your advice and doing my own thing. I think I just misunderstood what you were saying. Also, I'm not sure if it makes a difference, but I didn't use ColourB4, I did try the strand test like you suggested and it didn't really lift any colour so I decided against it.

If you bleach bath you will only lift a small amount depending on what peroxide and what ratio you mix, it may only lighten a shade or two at most.
If you apply the mix to all of your hair, it will all lighten the same amount, so it will be lighter but still uneven. So if you lighten two levels, the parts that are already light blonde will be over processed, the level 3 parts will lift to a 5, and the level 5 parts to a 7. The only way to even it out is to bleach the darkest areas more, either by using a stronger bleach mix on those parts or leaving the mix on longer on those parts
To get all your hair to an even blonde is a quite difficult colour correction. I would aim to only correct a third of your hair at a time. So starting with the underlayer, (with all the rest of the hair safely tied up out of the way)apply the bleach as needed carefully to each section, ie each inch wide thin strip of hair.
Did you strand test ?
How light are you aiming for?