Here are some entries from the Recent call list on my iPhone:
Why is one entry in red  and others in black? And, of the two entries in black, why does one have an illegible icon in the left margin? The first entry has neither a color nor an icon in the margin. What does that mean?
Unless you already know this, you can’t understand it. That makes it a poor UI. A good UI is obvious at first glance even to people who haven’t used it before.
Get rid of these unintelligible icons and color coding and just suffix each entry with one of “Outgoing”, “Incoming” or “Missed”, like this:
Once you understand whether a call was incoming, missed or outgoing, things are still not clear. Look at this entry:
My driver has two numbers. Which one did he give me a missed call from? Both are mobile, so the small clarification that says “mobile” is useless. It’s not clarifying anything. This should have been obvious to the designers. If someone has two mobiles, and you ask which one they called from, “mobile” is a stupid answer.
The obvious solution is to disambiguate with the number, like this:
Pandy Driver (9834984384)
Say “mobile” only if that person has just one mobile number.
In addition to telling you which number you got a call from, this UI also makes it clear which one you will end up calling back if you tap the entry. It solves two problems at once.
If you open an entry from the list by tapping the “i” icon, another mystery awaits you:
Now a third color — blue — has made its appearance! This is in addition to the red and blue from the recent call list. What does blue mean?! And notice at the top, it says that I made an outgoing call at 7:37AM. To which of the two numbers? It’s anybody’s guess!
Maybe they should add a striped purple color if the other person is also on WhatsApp. That would be obvious, right?
This is not a detective story. Nobody’s amused by this. People want to make calls with the minimum drama.
This screen also mixes up the contact entry with recent call information. In doing so, it does a poor job of both. Actually, the recent list said that I made a call to Godrej at 7:37AM. Why repeat that information in the contact screen? All it does is confuse.
Besides, instead of using color in this screen to (presumably) identify what number I called, present that information in the recent list itself:
Godrej (1800 0225511) at 7:37AM
That was all about the iPhone. Does Android fare better? Only marginally. Here’s the recent call list:
The bright colored arrows are more legible and clearer than the iPhone’s muted light grey ones. The fact that every entry has an icon also makes it more consistent and easy to understand. As opposed to the iPhone, where some entries have an icon and some don’t, and some are in red and some in black.
This UI still doesn’t tell you the order of the calls. Was the missed call the last one, in which case you should call back? Or did you already speak to Kartick after the missed call?
Note also that Ashok Mava has two mobile numbers, so saying you got a call from him is again incomplete information.
The designers of both iOS and Android have completely lost the plot on what should have been a simple, straightforward design problem. They’ve made it so complex that you need a PhD in HCI to understand this.
Fixing all this is simple: get rid of the arrow icons. Don’t show people’s names or numbers in different colors, like red, blue and black.
Suffix each entry with “Incoming”, “Missed” or “Outgoing”. If there’s both a missed call and an outgoing call , have separate entries in the recent list, so you know which happened most recently.
Don’t say a call is from a “mobile” number if that person has two mobile numbers. Instead give the number right in the recent call list. This goes for outgoing calls, too.
If someone called you from both their mobile and landline numbers, have two entries in the recent call list, so that you know you got calls from two numbers, and you can instantly call back on either number right from the recent calls list.
This would have been simple, straightforward and usable.
 Color-blind users may please go screw themselves.
 Or missed and incoming. Or incoming and outgoing. Any combination.