White, Green, Purple Aircraft

So, I thought I knew the difference. I thought the green ones were ADS-B, the purple ones MLAT, and the white ones Other. Other, being neither ADS-B nor MLAT, I would expect not to have a position or trail, however, in almost every case, I see both. Additionally, the information window at the top shows an MLAT position for these. So what really is the difference between the purple and white ones?

P.S. Of course, the color I’m referring to is the color of the rows in the table, not the color of the plane icon.

If a plane had ads-b data or mlat data, but hasn’t had a position in some time (60 seconds I think?), it will turn white. So white is really any aircraft that is getting mode-s messages but no recent positions.

Hmmm. That didn’t seem to be the case when I looked at the data. I’ll take another look later. I can’t now, because i have no whites. And that suggests something else. Maybe the whites happen when there’s too much data to process everything.

EDIT: OK, I got some whites. I notice now that there is a time in parentheses after the position, which seems to be the time since last position. I didn’t notice that earlier when I posted my previous message.