Explain darvas boxes?

why we have 2 colors in darvas boxes? help me to under stand darvas boxes.

trading strategy that was developed in 1956 by former ballroom dancer Nicolas Darvas. Darvas' trading technique involved buying into stocks that were trading at new 52-week highs with correspondingly high volumes.

A Darvas box is created when the price of a stock rises above the previous 52-week high, but then falls back to a price not far from that high. If the price falls too much, it can be a signal of a false breakout, otherwise the lower price is used as the bottom of the box and the high as the top.

Source: Darvas Box Theory Definition | Investopedia http://www.investopedia.com/terms/d/darvasboxtheory.asp#ixzz3saDUkKc1