System Tray Icon - change colour when disk cache fullfilling

[5erg]

I have 1 Gbps connection, and sometimes DL speed rises to 60 MB/s. I set my cache to 1,8 GB but sometimes (when i have multiple torrents to download) cache not flushing and uT crashes. I propose to fullfill uT's icons white area in systray by a red colour from bottom. It starts from 50% of write queue

 

Or any other solution for cache filling indication on systray's icon