There are so many other herbal options available for you but you probably didn't even know they existed!! You do not have to use man-made chemicals on your hair to change the color. Mother Nature knows what vain creatures we are. She gave us some healthy choices so we can indulge all we want while keeping our locks beautiful.
So lets go through your options. We're going to go from light to dark:
What if you have pale blonde hair or gray? Or what if you don't want to change your color at all but you simply want something that will heal the damage you've already done to it?
Zizyphus Spina Christi, also known as "Sedr" conditions, improves, and cleans hair without changing the color at all! Great for sensitive scalped folks or if you can't use commercial shampoos.
Blonde? Want to stay blonde but might want to tweak the color a bit? Or how about if you have brown or auburn hair and you'd like it to be just a bit lighter?
Cassia is the one you want. Cassia Obovata. It does have a slighty golden hue to it. But on most people when you use ONLY cassia on the hair you really can't see a difference in the color. It's when you add other things like henna that the real magic happens. Cassia is also known as 'neutral henna.' But it is not henna! Cassia is a completely different plant altogether. Cassia conditions, strengthens, and adds shine.
If you are trying to maintain or want to change to a simple brown with no red undertones then Buxus dioica is your answer. Also known as 'Katam.' Buxus/Katam has a GRAY dye. Now don't read that last part and get scared. What this means is that it essentially neutralizes the red in henna!! Keeps the brown and lifts the red out. Example: when you mix an equal amount of henna and katam together the end result is a plain brown. No brassy tones. No red, period.
All of these colors we've talked about so far are medium to light. They're on the upper end of the light spectrum.
What if you want to deepen the color? Make it a rich dark mahogany, black cherry, or the darkest black? Indigo is what you are looking for! Here is an indigo community to read and learn all of the finer points.
Indigo is a tricky little plant. It gives off a magnificent blue dye. So how exactly does one take a blue dye and end up with darker red, brown, or black hair? Henna. I'm not kidding. Redbrown and blue = black. Or at least it does in the world of herbology.
Let's say for example that you've got mousy brown hair and you want a deep dark cherry red. You're going to take henna and mix it with a bit of indigo. The more indigo you use the deeper the color will be. YOU control the color!
But what if you want a plain black? Please, ye gods, do not just slap a slushy bowl full of indigo on your hair. You will wind up with blue hair. The trick is to use straight henna on your hair first. Rinse.... rinse some more... and then you add pure indigo. Voila! Raven black hair. Shiny and healthy.
So you see, you can use Mother Nature's gifts wisely and enjoy a chemical free hair color. No more itchy scalp. No more "but they discontinued my color" whining in the hair dye isle. (Oh I am soooo familiar with that particular nasal tone emanating from the haircare section. I, myself am guilty.)
My own freezer has a ziplock bag full of individual baggies of pre-made henna. It's my own recipe stuff. When I want to freshen up my color or I feel like I need some pampering, I grab one of those individual baggies and lay it in a bowl of room temperature water. Once the henna mix is at room temp I put on my gloves, cut open the bag and apply it to my hair. (And I don't have to open a window so I don't die from the fumes, either)
No chemicals. No fuss. No allergies. Healthy hair.