What do the colors mean in htop?

For the CPU cores, I think that blue means nice, green normal CPU use and red I/O. But I'm not sure and I haven't found a definite answer.

Then there are the colors for memory. What do green, blue and yellow mean there?

2 Answers

Press h inside htop for quick help.

CPU

Blue : Low-priority threads Green : Normal priority threads Red : Kernel threads Turquoise : Virtualization threads 

Memory

Green : Used memory Blue : Buffers Yellow/Orange : Cache 

Also, in the list of processes, there are some that appear in Green. The black ones are main processes and the Green ones are threads. In my example below, I'm running a repair on a Cassandra node and as we can see most entries are threads.