Change behavior for tab-key (autocomplete) when cursor is placed right after colon

Change behavior for tab-key (autocomplete) when cursor is placed right
after colon

I want this...
html,body{
padding:/*tab-key-pressed!*/0;
margin:/*tab-key-pressed!*/0;
}
...to become this:
html,body{
padding: 0;
margin: 0;
}
But instead I get an auto-complete like this:
html,body{
padding::;0;
max-resolution: res;0;
}
I've been looking at the css_completions.py, but I've never learned python
and I'm not man enough to make sense of things. :(
So to sum up things: Is it possible to selectively disable auto-complete
when the cursor is after a colon?
Thank you for your time!