problem is that terminal used doesnot support color scheme used by cqlsh

on cli use

--no-color  

https://cassandra.apache.org/doc/latest/cassandra/managing/tools/cqlsh.html#command-line-options

or specify in

~/.cassandra/cqlshrc

[ui]
color = false

https://cassandra.apache.org/doc/latest/cassandra/managing/tools/cqlsh.html#cqlshrc