First, you should try to edit Font and Colors from your dashboard, most of my templates are compatible with new template designer tool, so you just go to: Design > Template Designer > Advanced
If this not work, this means you are using old blogger templates, but this OK, the template works perfectly.
Now let explain how you can edit your color and font direct from template source:
Change Font Color
1. Design > edit HTML
2. Search [CTRL+F] for: body {
3. After you find it will see usually color:#333333
4. This is color of your text, change it from #333333 to #ff0000 [you will see difference]
5. You can do many search [CTRL+F] for the word color: to change color link etc
Change Font style
1. Design > edit HTML
2. Search [CTRL+F] for: #outer-wrapper {
3. After you find will see something like: font: 14px Arial; or font-family:Arial;
4. Replace it with your favorite Font [Georgia, Helvetica, Times, etc]
Usually I use diferent font for Header, so to edit and header font search for #header h1 {
Hope I explained as simple was possible, if you have any other question let me know, but remember that latest templates and new ones will have option to change font and color from blogger dashboard [Design > Template Designer > Advanced]