There is no Color Overlay keyboard shortcut but you can add one. Go to Edit>Keyboard Shortcuts and add one. (outlined in red)
And yes there is a keyboard shortcut to switch between the layer and layer mask view. In your layers Alt click or Option click on the layer mask. (outlined in red)
Hven i means "Shortcut for switch between layer and layer mask, I means a keyboard compination I can press.
If the layer is active and I press "CTRL-SHIFT-M" the Layer mask be active insted off, and if I press ""CTRL-SHIFT-M" again the Layer be the active again.
Switches between layers and layer mask by using shortcuts
The shortcuts should be indicated in the Channels Panel.