troubles with color black in illustrator

Hello i have troubles with  Illustrator. The thing is everytime i make something with illustrator tools (also type) it allway makes it some greyish color (sometimes even different type of grey - sometimes a bit greenish or blueish..). If i want to change it to other colors it works fine, but when i try to make it black and not greyish it allways turns right back to that grey but it never changes to black. I have problems working because of that and nothing helps. This occours in rgb or cmyk it doesnt matter the document color mode.  Thank you for help