How can I Colorize my custom .bashrc file w/ nano in shell

im using an arch linux variant with xfce, opening up a terminal shell and running **sudo nano .bashrc** I can see the file is colorized despite there being no headers referencing a schema. Looking inside dir ***/usr/share/nano-syntax-highlighting/*** shows no file for bashrc configs I would like to use the same colors that are used for**.bashrc** for my **.customrc** file. How and where can I set this?