Heat maps are great because they can show you which pares are trending in a direction more strongly then others.
Few ways you can use the heat map.
1) Is there a pair that DARK Green or Red on the larger time frame? that means its trended strongly lately for a longer period of time. If the lower time frame is changing colors in the other direction, you can use that to look for pullbacks or even large reversals.
2) larger timeframe starting to lightly change colors in a direction making a possible new trend? Is the lower timeframe starting to match the new larger trend? Signal to pull that chart up and look for trend continuation trades.
Hope that helps.