Median Momentum with Buy/Sell Signals and Bar Color

Momentum Calculation:
Momentum is calculated as the difference between the current close price and the close price momentum_length periods ago: momentum = close - close.

Highest and Lowest Momentum:
The highest and lowest momentum values over the specified length are calculated.

Median Momentum:
The median momentum is calculated as the average of the highest and lowest momentum values.

Color Setting:
medianColor is set based on whether the momentum is above, below, or equal to the median momentum.
barColor is set similarly for bar coloring.

Plotting:
The script plots the median momentum and the actual momentum values.
Buy and sell signals are generated when momentum crosses over or under the median momentum.
The script also plots the buy and sell signals with arrows on the chart.