The post contains a question - accompanied by the answer to the question. The question should be viewed, without the answer being visible, to make the reader think about the answer. This is called, by many, a "spoiler".
Neither of the latter scenarios make the post a lot of fun to read.
If the blog posts have a solid white background, you make the post text white.
Examine a post, in my text blog.
Two spoilers - both blank.
Click and drag across the first spoiler - and see the first answer.
Click and drag across the second spoiler - and see the second answer.
The spoiler code is not complicated.
What would YOU do?
What Lancelot chose is hidden. But - make <span style="font-weight:bold;">your</span> choice before peeking. To see the answer, highlight the area indicated, by clicking the mouse and dragging the cursor between the arrows.
The answer is here ==><span style="color: rgb(255, 255, 255);">Noble Lancelot said that he would allow <span style="font-weight:bold;">her</span> to make the choice herself. Upon hearing this, she announced that she would be beautiful all the time because he had respected her enough to let her be in charge of her own life.</span><==
Now - what is the moral to this story? To see the answer, highlight the area indicated.
The answer is here ==><span style="color: rgb(255, 255, 255);">If you don't let a woman have her own way, things are going to get <span style="font-weight:bold;">ugly</span>.</span>==
Hoping that your blog does not use a semi transparent floating background over a multi colour background, just make the text the same color as the background. Then, instruct the reader to click and drag the cursor, to highlight and make the spoiler visible.
An easy way to hide content is to make the text the color of the background. The reader can click and drag, to highlight the text, when then is visible.