Update TriceUserManual.md

In 4.8 corrected: letter -> message

Author: rokath

docs/TriceUserManual.md

@@ -524,7 +524,7 @@ Trice is usable also inside interrupts and [extended format specifier possibilit
 
 ### 4.8. <a id='tags,-color-and-log-levels'></a>Tags, Color and Log Levels
 
-You can label each Trice with a tag specifier to [colorize](#trice-tags-and-color) the output. This is free of any runtime costs because the tags are part of the Trice log format strings, which are not compiled into the target. The Trice tool will strip full lowercase tag descriptors from the format string after setting the appropriate color, making it possible to give each letter its color.
+You can label each Trice with a tag specifier to [colorize](#trice-tags-and-color) the output. This is free of any runtime costs because the tags are part of the Trice log format strings, which are not compiled into the target. The Trice tool will strip full lowercase tag descriptors from the format string after setting the appropriate color, making it possible to give each message its color.
 
 Loggers use log levels and offer a setting like "log all above **INFO**" for example. The Trice tags can cover that but can do better: Inside package _emitter.ColorChannels_ in a single file [./internal/emitter/lineTransformerANSI.go](../internal/emitter/lineTransformerANSI.go) all common log levels defined as Trice tags alongside with user tags. The user can adjust this. The Trice tool has the `-pick` and `-ban` switches to control the display in detail. Also a `-logLevel` switch is usable to determine a display threshold as tag position inside ColorChannels.