If you want to change the design of your blogs, goto Dashboard - Design and then Template Designer you will see the above screen, In the first screen you can change your Blog templates, you can change the background picture of your blog.
In Template Designer the above screen shows background settings of your blogs, such as if you want to change the background color of your blog, you can change it from here, if you want to change the background picture, blogspot give you lots of pictures and devide it in defferent categories such as if your blog is related with business you can choose Business category and you will find lots of pictures related with business and in the same way if you select family the pictures will be related with family etc
If you want to change the main color theme you can do it from here, if you change your blog color and later on want to restore your previous style, just come here and click on "Use default background and colors? its so easy.
If you want to change the width of your blog, such as if you want to give more space to your postings rather than to give the right side column, you can do it from here.
Changing Layout of your blog is one of the Best feature of blogspot, if you want to change Layout just come to that area, here you will see different blog layouts, such as with no columns, with one right side column, with three column, etc.
Last option is Advance, in that screen you can realy change the look of your blog, you can change each and every thing in your blogs, it will show you each category such as Page texts, backgrounds, Links, Blog Title, Blog Description etc if you can click on Link then the next option is Font Style you can give diffent styles of fonts to your blogs, if you want to Bold the Link you can do it from here, if you want to increase the size of Link you can do it from here, next option is Colors, you can give any color in the boxes to your Links, select the attractive color which are more suitable with your blog colors because its very neccessary that you can choose the colors in such a way that your readers can find the things easily and comfort to read your postings easily, more colorful site simetimes will ruin your visitor