Changing texture brightness on Android in Opengl-es

Question

Hello,
Firstly I must say I'm green as grass in opengl subject.
I'm writing simple 2-d game for android using opengl-es. I use GL11Ext.glDrawTexfOES() to draw the textures (just like in one sample code named 'sprite-method-test'), and gl.glColor4f to color them (and set transparency). But I'm completely helpless if I need apply some brightness or contrast to the rendering texture.
I really appreciate any help.