Hi and welcome.  Hair color can be a lot of learn about and consider so it's great you are asking questions and gathering your information before you start.

 

Highlights generally lighten the base color 2-3 shades.  Lowlights usually take the base darker 2-3 shades.  The key factor to consider is that if your hair is already very dark, if you lighten it 2-3 shades, you have to be careful not to pull unwanted colors like red, as an example. 

 

Highlights almost always require that some sort of lifting agent be used to lighten the base.  Once a lifting agent is used, the color will be permanent and will remain until the hair regrows.  In other words, you will have roots the same color as your natural hair color. 

 

So if you highlight and then don't want the natural root regrowth then you would have to color the base darker to remove the highlights.

 

When a lifting agent is applied to lift the color then the lifted sections can be colored with complementary shades such as caramel, milk chocolate, plum, dark brown.

 

Some hair colorists do use semi-permanent colors when they are doing highlights and lowlights but of course a lot depends on the color of they base they are working with.  If the starting base is dark brown or black then semi-perm may or may not be an option.

 

In your case, since your hair is naturally very dark you would have to use some type of lift/lightener in order to create contrasting hues.  This will not be temporary.

 

If you are unsure I would suggest that you get a few strands of fusion hair extensions applied around your hairline in the hues you are interested in adding such as plum or milk chocolate.  A few strands of fusion hair extensions would be inexpensive and it would allow you to change up your hair for awhile but allow you to easily remove the extensions when you are tired of it.

 

Also, if you go with fusion extensions for a trial run, if you don't like the hues you can either try other colors or decide you are happy with your hair the color it is naturally.  A lot less danger of damage.

 

Finally, curly and/or wavy hair has a cuticle which never completely closes.  The process of coloring hair requires alterations in such a manner as to leave hair more dry.  Since curly/wavy/textured hair is naturally dry and coarse, this only makes it worse.

 

Hair color is definitely an option for curly hair.  Lorraine Massey whom I had the pleasure of meeting in the past has gorgeous natural curls and they are highlighted.  Her highlights are painted onto her hair when it is full of curls and it is gorgeous.  But her natural base is very light.

 

I would suggest if you don't want to get a few extensions that you play with a set of 10 clip-in extensions and play with them instead.

 

Once you commit to coloring your hair it is a long term process.  I am not advising against coloring your hair.  I have worn my hair highlighted and lowlighted for years and I love the results.  However, it is a big committment of time and funds so take your time before you jump in.

 

Also, if you decide to get highlights/lowlights please go to a hair colorist the first time.  Don't get me wrong.  I love hairdressers.  I went to cosmetology school myself.  However, color is complex and some hairdressers are generalists rather than specialists.  Find a hairdresser who specializes in hair color.  With hair as dark as yours its important that it be colored properly to prevent damage.

 

There are tons of great people with hair color knowledge who visit HairTalk so hopefully some of them will jump in with other tips.

 

Good luck and let us know what you decide to do.