I soaked each piece of fabric and put it scrunched into a plastic bag. The fabric was wet, but not dripping wet. In a cup I put silver and white acrylic paint - for the black fabric - and diluted this with water. For the blue fabric I used gold and magenta. Using a bristle brush I pounded the paint all over the fabric. Closed the plastic bag and put it into a container on top of the heater in the sunshine. Both bags remained like that for about a week. For the second week I opened the bags a bit and again left them there. After 2 weeks the fabric was dry enough and this is how the black one looked when I took it out of the plastic bag:
I am not a scientist, but I do know that the warmth creates the capillary reaction. The paint starts creeping up in the folds and remains there while the fabric dries.