Can't see textures I draw, on windows and android

i'm using unity 4.5.3f3 free version

• i create a simple texture2d by code , with the size of 200 x 200 and the color black

• i try to draw the texture on screen using GUI.drawTexture and Graphics.drawTexture

• in the unity editor i press play and i see the texture (but its white, not black)

• I build and run on android, and i don't see anything (I test on samsung galaxy note 3)

• I build and run on Windows, and don't see anything

• for testing, i created a simple cube in the center of the screen using GameObject > CreateOther > Cube.

• I see the cube just fine on all platforms.

help