I'm trying to write different parameters into my Source Text like this:
But It shows [object][object] instead of showing text of two layers A and B.
What should I do?
You cannot combine different text styles within the same layer and that is that.
Can I set different colors for text within the same layer? Means color 1 for text 1 and color 2 for text 2?
Using the Animate menu (visible when you expand a text layer), it's possible to add a Fill Color. From there, if you expand the options and the advanced options, not only can you set different words to be different colours, but you can add multiple animators and keyframe the change.
That's what text animators are for. I suggest you read the online help on the subject.