@Falstaff I actually did not say that, in fact I said what you did, which is not that volume is 'predicted by price' but rather that a horizontal volume graph does a better job at relating where that volume is concentrated in relation to price levels, rather than the ordinary vertical volume bars below your currency chart...
Here are two examples: one sent to me by my contact here in the city where I live, @BrentJB , who has a subscription to TradingView and kindly sent me a Volume-At-Price chart (daily) screenshot for EUR futures (CME) four days ago:
Another type of volume-at-price analysis, called TPO (time-price-opportunity) is shown in this video in 2015 by the very person who started this thread, namely @emeraldorc , who is actually Daniel Sesay and now works with the Traders' Club in London:
He also posted volume videos earlier in this huge thread, back in the very first pages, so if you scroll back you will
In terms of the volume bar colours on the Euro futures chart, I believe that green and red turn darker as the volume increases over a certain amount: what is important is seeing the biggest concentration, in this case around the 1.18 mark, which indeed could be how we saw price trying for 1.1850 but finally retreating and, today, completely collapsing all the way to 1.1550.
I hope that this helps!