Restoring old photographs always present different challenges.  In this case, the colours were restored using three different techniques.  The 40-year old image was faded.  Like most colour photographs, the differnt colours do not fade at a similar rate.
 
1.  The background was actually re-colourized.  There is not much software available to do this.  It is not simply a matter of changing the colour to the desired hue.  Subtle variations in toning, and luminance need to be taken into account.  I use a software called Codijy (link here).  It does a great job but is very CPU-intensive, and it took nearly 10 minutes of processing just to colorize the wall.

2.  The clothing just needed some simple adjustments in photoshop (levels, brightness, contrast, and hue)  This was the easiest part of the restoration

3.  The skin tone was more difficult.  As there was really no magenta/red toning left in the image, the skin had become too yellow.  Changing the hue/color just for the skin, and adjusting for contrast, etc.  I was able to get a good approximation of the actual skin colour.

Next time I'll give some examples of B&W restoration.

I know: it doesn't look like much.  But here's the point:  This painting is about 32' wide, and about 42" tall.
The frame is a very simple, straight profile with a white satin lacquer.  So what's so special about that?  Well, the moulding is 3 1/2" wide.  Those mitered corners have to be exactly at 45 degrees, else you're going to have gaps showing.  That's not something you can do with a $100 saw from Home Depot.  Our double-mitering saw is almost 40 years old, but it does a beautiful job.  And what a beautiful painting, done almost fifty years ago as a self-portrait.