for turbulance detecting radars (for ex on 737) magenta has nothing to do with quantity of water in clouds.It just indicate a diference of water particles velocity of more than 5 m/s horizontaly. I've once seen only green returns on radar,and when we switched on WX/TB (ATIS says windshear reported) all green become magenta,and indeed it was turbulance
Red signify the most amount of water in clouds,heavy rainfall.Sometimes,there is no turbulance associated with red,you just deeply wash your plane.
You should always use tilt combined with diferent ranges to asses the potential danger in a cloud.You can enter in red (although it should be avoided due to heavy water ingested,hail and usual turbulance) but avoid by all means the magenta cell.It will give you ,at least,a big scare and maybe some injured passangers.And scare most of them of flying for months,at least.
Brgds Alex