Clearly it's not arbitrary when LookIntoBitcoin have modified the logarithmic curve, and haven't referenced the fact it's arbitrary or lacks any scientific basis. Probably because it's a mathematical based curve, nothing to do with science. The irony being that a logarithmic curve in itself isn't arbitrary, it's simply how you style it (connect the dots), even if the original remains arbitrary and unchanged.
You didn't get me. The Log curve is an approximation of price history (logarithmic regression). That is the scientific part. But the rainbow is made by duplicating that curve parallel to itself with certain intervals that are not somehow "scientifically" linked to volatility, ATHs ant Lows.