If the coloring of the bar is the main concern here, just letting you know you can change the colors for individual sets using themes. So I think if you add two sources, and change the color for hot water, you’re mostly there.
hm… I am not sure, if this will work as expected.
Afaik, you can define the bar-colors for the chart but taking the chart from the energy usage as example, Grid is “blue” / solar “yellow”…
I can only change the colors for Grid / Solar - and they will then use a differen schema based on my settings.
And for water, this is exactly the same - since I cannot setup a “cold water” meter and a “hot water” meter.
Both would just be 'water" - and therefore using the color defined in the theme.
I will try to setup an example, just need to create a “demo meter”