If you want to, you can add some color to your text. Only people with client compatible with mIRC colors system will be able to see your colors.
All you need to do is to bring up the context menu of the text box. Long press on it, and choose “Customize text”.
Starting with AndroIRC 3.1, a color-wheel icon is present on the right of the text box. Just click on it to popup the customize dialog.
Just hit back to close the dialog.
You can't have your colors choice to be automatically applied when you start typing text. Don't forget that colors should be used a little and are very annoying for people reading you. That is on purpose and won't be changed!