This script allows you to input 2 different coins and plot % changes against each other.
Look Back is adjustable to account for different time frame windows. Default is 1, so each line will be graphed on a 1:1 ratio with the candle period selected on the chart. raising this number to 24 will plot the change across every 24 candles and so on. It's pretty interesting to move the input dialogue window out of the way and change this number, watching how the % gain comparisons change in real time.
Default coins to compare are set to BTCUSD and ETHUSD @ coinbase.