Yes, It can change color and become green or blue. However, if it is done right with the right concentration of the pigmenta and proper color, the risk of discoloration is very minimal. We prefer non permanent pigments for the same reason. They may fade but usually don't turn blue.
It´s impossible to say without clear images. But one factor is going to be the contrast between your skin complexion and the pigment tone used. It maybe simply the pigment stands out too much from the surrounding hair and looks unnatural. Basically does not add to the look of fullness just sits ...
Meeting real scalp pigmentation patients is a great way of checking on the quality and work of a SMP technician or Doctor. Especially if they have a similar skin complexion to you. As this can change the pigment application. Also, the hairline design as this can alter greatly. A natural design...