Colours: Pretty plain. You have some nice colours in your header - why don't you build on them? The header should 'set the mood' for your blog and correspondent with the rest.
Typography: Your should make your headlines bigger and more prominent. Makes it easier to jump from one entry to another. Give the lines between headlines and navi texts (date, author etc.) more space to breath. Looks all a bit squeezed.
Layout: I find the balance and proportions not very smooth. The main area is to wide for the small font. Makes it hard to jump from line to line while reading.