It's not uncommon these days for the terminals attached to serial consoles to support ANSI escape sequences. However, we assume escape sequences may break some serial consoles and default to not using them when boot_serial or boot_multicons (or if console contains "comconsole" in the forth loader) for broader compatibility. We also have loader_color which can be explicitly set to "NO" to disable the use of ANSI escape sequences.
The problem is that loader_color=YES gets ignored when boot_serial=YES or boot_multicons=YES (or when console contains "comconsole" in the forth loader).
To fix, the existing default behavior remains unchanged when loader_color is unset, loader_color=NO explicitly disables the use of ANSI escape sequences still, and the change is that loader_color=YES can now be used to explicitly allow ANSI escapes when a serial console is enabled.
Sponsored by: iXsystems, Inc.