Her style has been described as androgynous but can also look quite feminine.
In the photo above she is wearing wide trousers, a blouse/shirt and wedge sandals. We can take elements of this style of dressing (without the socks) and translate it into 'today'. The clothes below are from Marks & Spencer (wide-legged trousers) and Boden (shirt and sandals):
As you can see, what Katharine Hepburn wore in the 1930s/40s hasn't dated that much - those wide-legged trousers, shirt and wedges can easily be found in 2015!
Many of the stars of yesterday (including Katharine Hepburn) whose style we find inspirational and who I've mentioned on the blog, such as Audrey Hepburn and Grace Kelly, kept to timeless, classic clothes which can be repeated down the years. I admire them for that.