Colour b4 help!

How many times did you wash your hair between dying and using the color b4?
There is a possibility that you still had the old dye molecules in your hair and they re oxidised when you used the peroxide dye.

Since I used colour b4 I washed it about 4-5 times the last time I washed it was Saturday and I did notice it still had a bit of the usual colour b4 smell to it even though it was about 2 weeks since I stripped it.

It sounds like either re-oxidation, where the old dye molecules are activated by the peroxide in the dye, or that your hair is very porous so the colour turned out much darker than expected.

Is there any way to prevent this from happening? I'm planning on using colour b4 again to remove this dark colour and I don't want to end up with dark hair again when I dye it. Also should there be a certain amount of time I should wait before dying it?

some people/hair types seem more prone to it. Make sure you rinse really well with really hot water, keeping the hair moving in the water. Then you can check if all the colour molecules are rinsed out by putting plain developer on a strand. If it doesn't go darker you have rinsed all the dye molecules out.
A week is usually the recommended time to wait, but I would always wash it several times whilst waiting. (I only wash mine once a week)

Since my hair still smelt of colour b4 even after I washed it a few times I thought it might not  have been rinsed out properly. I'm planning on stripping it again next week and getting a developer and tint from Sally's to dye it with. Hopefully if I try what you recommended it will work.

I would personally use a dye with no peroxide. Not only does it lower the risk of reoxidisation but you have already dyes your hair once recently and another dye with peroxide could really damage your hair.
check out the Adore dyes; they have a nice range of natural colors.

Oh brilliant I must check them out. I was actually thinking that when I was letting the colour b4 develop I blasted my hair with a hairdryer to speed up the process and I wasn't too sure if that may have been a cause for what happened to my hair.