What exactly do the colors in htop status bars mean?

Hitting F1 or h will show you the key. But for reference, the default colors are:

CPU:

  • Blue = Low priority threads
  • Green = Normal priority threads
  • Red = Kernel threads

Memory:

  • Green = Used memory
  • Blue = Buffers
  • Yellow/Orange = Cache

There are a couple of different color-schemes available, you can see them through hitting F2.


I couldn't find this documented elsewhere. Looking into the code:

There are two modes for CPU metrics reporting: the default one, and a "detailed CPU time" which can be enabled from the Setup screen (Display Options / Detailed CPU time). All of them show the percentage of time spent in different processes:

Default mode

  • Blue: low priority processes (nice > 0)
  • Green: normal (user) processes
  • Red: kernel time (kernel, iowait, irqs...)
  • Orange: virt time (steal time + guest time)

Detailed mode

  • Blue: low priority threads (nice > 0)
  • Green: normal (user) processes
  • Red: system processes
  • Orange: IRQ time
  • Magenta: Soft IRQ time
  • Grey: IO Wait time
  • Cyan: Steal time
  • Cyan: Guest time

Memory meters are more straightforward:

  • Green: Used memory pages
  • Blue: Buffer pages
  • Orange: Cache pages
  • Grey: Free (unused)

Note: Info obtained from htop source code at https://github.com/hishamhm/htop/blob/master/CPUMeter.c .