As for the visualization we were thinking of a world map , with all countries having a tool tip denoting the consumption based emission for electricity.
A map is a good idea. Maybe countries could be coloured differently depending on various criteria (e.g. how green they are, how high is their total CO2 emission, how high is their CO2 emission per capita, and so on...).
Yes the color will be based on a linear scale i.e. dark red to light red for emissions.As for the framework most popular options are react and angular. React has lots of packages available that can be used like react bootstrap, d3 for react and so on. It implements virtual dom based alterations making the process very fast. Other alternatives are angular 2 and vue.js.
@bruno-wp react also has a really good community support to it. There are also some great tools/extensions available to help with the debugging of the components.