Update: This post was written for the old post editor and not for the updated post editor. You can toggle between the updated post editor and the old post editor by going to SETTINGS > BASIC and at the bottom (Global Settings), tick your preferred post editor. The new post editor especially in the edit HTML mode has very few icons. There are no filmstrip icon (video upload) in the new post editor
It has happened a few times in the past that bloggers complained that suddenly those icons in the Blogger post editor for specifying the color, font type and size have disappeared. Now if previously the toolbar in the post editor had looked like this (see screen shot):
but has changed to this (see screen shot):
then the problem is easily solved. What has happened was that previously the post editor was in the compose WYSIWYG mode which has a longer toolbar with more tool icons but somehow the blogger probably got changed into the edit HTML mode which has a shorter toolbar with less icons. All you need to do is to change back to the Compose mode if those extra tool icons are important to you.
However, my advice to you if compose WYSIWYG mode is what you prefer is to switch over to the edit HTML mode as you can do more and have better control over your blog.
Missing toolbar, distorted unusable post editor
What to do when you don't see EDIT HTML/COMPOSE tabs
Cannot see toolbar in post editor - what to do