Best colours for my natural hair?

Semi permanent dyes dont really stick to virgin hair for very long. The best i've found was manic panic which stayed for 4 washes on my virgin hair bt it depends on hair type really.
My guess a to what you were allergic to is PPDs. They are in most box dyes and people can become allergic at any time. Even if they have been used before. They are quite harsh chemicals. You could try lightening with just bleach or a bleach bath. And do a patch test before.
Most semi permanent dyes are vegan frendly as they are made from natural ingredients so it should be ok with your baby. My little cousin used to try to eat my hair all the time.

I've only used reds on unbleached hair and (although I'd prefer if the colours came out brighter) I was still quite pleased with the results. My natural hair is around shade 4 (maybe 5) brown. I've tried MP Wildfire, Rock N' Roll Red, and Infrared, which worked very well, and also adore paprika and Cajun spice, which I wouldn't reccomend on unbleached hair. I found that after a month the colour still showed up but it was a bit faded, so I had to re-dye it. Even though I heard Manic Panic doesn't last well I was impressed by how long it lasted. I dyed my hair in summer and I still have sections of my hair that are slightly red! (But I think that's because they got stained). I guess I was lucky with the results and they depend on each person's hair.

Although I haven't used these colours, I've heard greens work quite well on unbleached hair. Dark blues can come up as blue-black, however if the blue is lighter it can come out green. I'm guessing other dark colours, such as dark pinks, work well.

Unfortunately, these dyes don't stick to grey hairs very well, as they are very resistant. The colour will just come out pastel looking. Using peroxide to pre-soften hair would help with this, however, you may not want to do this.