Saiyan
This is the regular saiyan stage. At this stage the saiyan looks like a regular human, but is way stronger. All full blooded saiyans have black hair, and their hair doesn't grow. The half-breeds on the other hand don't always have to have black hair. Examples of this are Trunks (purple hair adopted by his mothers side). As for gohan, pan, and goten, they have black hair because both of their parents have black hair. Make sense? You are probably thinking "Hey, whos that dude in the picture, he has black and purple hair." This is becuase it is a fusion of goten and trunks. You will learn about the fusions on the fusion section.
Super Saiyan Lv.1
To make it to this level for the first time the saiyan needs to be enraged. Their eyes turn green, their hair is up and yellow. At this stage their speed and strength increases. The first saiyan to reach this stage is Goku. He gets really mad at Freiza for killing his best friend Krillin. Later on this stage was reached by Vegeta, Goten, Trunks, and Gohan as shown above. Also the fusions of Gogeta, Gotenks, and Vegetto. Basically all of the saiyans shown later on (after the Freiza saga) are super saiyans or are going to become super saiyans.
Super Saiyan Lv.2
This stage makes the saiyan very, very strong compared to the other stages. Also to make this stage the saiyan has to be extremely enraged. Their eyes turn a different shade of green, their hair is up and spikey. Also their muscles are bigger than in super saiyan 1 stage. The first saiyan to reach this stage was Gohan in the cell saga when he released all of his rage and turned it into energy. Also while in this stage you hardly would ever see the saiyan smiling , he is usually very angry at this stage. This stage was later on reached by basically all mentioned above.
Super Saiyan Lv.3
This is my favourite stage of all the super saiyan levels. All of the saiyans that reached this stage didn't even need to be that mad, kind of awkward isn't it? At this stage their eyes are a teal colour and their hair is grown down to their waste. Also their muscles are very huge and their speed increases greatly. I would also like to put that their speed increases WAY more than the other stages (1, & 2) The saiyans that have reached this stage are Gotenks, and Goku. Goku reached this stage first and this was in the other world. I would also like to input that Gotenks is stronger than Goku in this form becuase Goku gets really weak and tired quickly after turning ssj 3.
Super Saiyan Lv.4
This stage of super-saiyan was only reached throughout the dragonball Gt series which most of you have probably heard of. In this stage the saiyan looks like a monkey. Their hair is black, long, and they have fur all over their chest. At this stage if the saiyan was missing his tail will grow it back, but only for the short time that he is a ssj 4. Also their eyes seem to have a thick red lining around them. To reach this stage the saiyan has to become Golden Oozaru. To reach this stage the saiyan must look at the Earth from a distance, then they must be able to control golden oozaru. Goku and Vegeta becamse ssj 4 but Vegeta cheated by using the Brute ray that Bulma made for him.
