Help! How can I change the stroke/fill color?

[tomokoxf]

Suddenly ( I must did something, but I don't remember), my stroke color is white. So when I tried to write a circle/rectangles, it did't show anything. Them, I opened my saved file which background was some other color, I could see the white circle. Now, I cannot even fill the color in the circle. How can I change?

[Angel135612]

What software are you using??