How to flag list of cities based on continent?

I have a two-column list of cities and continents:

Prague; Europe
Berlin; Europe
New York; America
Tokyo; Asia

How can I show only the citites conditionally flagged based on the contintent value?

Something like this:
<red flag> Prague
<red flag> Berlin
<green flag> New York
<yellow flag> Tokyo

Any help would be appreciated!

Thanks, newdoverman,
but it's not exactly what I meant. I'm familiar with conditional formatting of this type. What I want to do more specifically is to add an icon. Conditionnal formatting offers some bullets, flags and other icons, but they only work with numbers. You cannot use them with texts or, in my case, with references to other cells (it's the cities I need to have flagged, based on continents).
Thanks for the tip though.

You suggest to add a new column, do I get you right? I hoped to be able to have the cities flagged in the same cell.
Actually, the cities was just an attempt to simlify things that might have worked the opposit way. I have a list of clients and I want to flag those overdue... I should have said it this way in the first place - sounds so much more obvious.

I try to avoid using extra column, it would indent the clients' names and I need to save space. So i want the result look something like this

Prague
Berlin
o Moscow

rather than (the dots simulate the indent):

...Prague
...Berlin
o Moscow

I also was considering using an extra leading character or symbol. But this would be a connected string and I don't know how to change the font to the leading character of such a string, let alone depending on the first character's value.