God bless text config files!
I've managed it somehow.
I decided that the best way to walk around (unknown for me) C::B procedures of configuration - to edit config files.
So I edited ~/.config/codeblocks/default.conf in a part of Compiler for MSP430:
<msp430_gcc>
<NAME>
<str>
<![CDATA[MSP430-GCC-OPENSOURCE (SOMNIUM Technologies)]]>
</str>
</NAME>
<COMPILER_OPTIONS>
<str>
<![CDATA[-c -g -Os -Wall -ffunction-sections -fdata-sections;]]>
</str>
</COMPILER_OPTIONS>
<LINKER_OPTIONS>
<str>
<![CDATA[-Wl,-Map,${PROJECT_DIR}${TARGET_OUTPUT_FILE}.map;]]>
</str>
</LINKER_OPTIONS>
<INCLUDE_DIRS>
<str>
<![CDATA[/home/tkm/ti/msp430_gcc/include;/home/tkm/ti/msp430_gcc/msp430-elf/include;]]>
</str>
</INCLUDE_DIRS>
<LIBRARY_DIRS>
<str>
<![CDATA[/home/tkm/ti/msp430_gcc/include;]]>
</str>
</LIBRARY_DIRS>
<MASTER_PATH>
<str>
<![CDATA[/home/tkm/ti/msp430_gcc]]>
</str>
</MASTER_PATH>
<C_COMPILER>
<str>
<![CDATA[msp430-elf-gcc]]>
</str>
</C_COMPILER>
<CPP_COMPILER>
<str>
<![CDATA[msp430-elf-g++]]>
</str>
</CPP_COMPILER>
<LINKER>
<str>
<![CDATA[msp430-elf-g++]]>
</str>
</LINKER>
<LIB_LINKER>
<str>
<![CDATA[msp430-elf-ar]]>
</str>
</LIB_LINKER>
<DEBUGGER_CONFIG>
<str>
<![CDATA[gdb_debugger:Default]]>
</str>
</DEBUGGER_CONFIG>
</msp430_gcc>
...and made msp430_gcc a default Compiler
Maybe there are some minor errors or rather non-efficient code - it's not as important as the fact that the C::B accepted the changes.
Thanks to oBFusCATed for the hints! You made me to read a little - and I found a very useful way to set editor colors. In the previous life I used to create all colors manually. But now I've imported that beautiful file with themes and set my favorite dark one. The only thing that spoils the evening is: I cannot highlight the current line... Well, it's for tomorrow.