light level tool

in regard to the new caves and the opertunity to build in them it would be ideal to ether have a function ability or a tool that would give the ability to view the light level with a cross or other logo marked on the block that would indicate that blocks light level, ether a single logo or marker with different colours, or more friendly a different shape besides colour, it would make it far easyer to find light level on a large scale, wich would have been far easier, and with light levels edmited a colour for when the light level is under 7 and one for when its light level is alterd by the sun