I was inspired to do something similar with the children at preschool.
The first step was to cut and/or tear different colours of tissue paper.
We used our clear perspex easel instead of a window.
Different kids arrived at different times and added their tissue paper to the easel.
I had envisioned (a la filth wizardry) that the easel would be completely covered like this:
But the children had other ideas.
They carried over other collage materials and added them to the mix:
Although it didn't turn into a stained glass window it still succeeded as a communal collage experience - and this week it will turn into a communal washing up experience!