Can we write in posts with colored letters like this ? Ex: Hi everyone..! is it a spam..?

Well i think if you type just "Hello Everyone" without the exclamation and the dots i dont think it would be spam.

No but it sure is obnoxious :/

It is not spam and spam is when you post a post something repeated for example ffffffffffffffffffff <------ that is spam

Ok... I thought this will also a spam. If i write fullstop or exclamatory mark(!) then is it a spam ?

Lol for a second i thought this thread is a spam :P
Btw it is what you wrote is not a spam but if you write that on threads that do not require it or if you write only that on threads it can be considered as spam.

it really depends on how you'll use it. basically, you might use it if you are designing your contest or market thread. but if you are just going to use it in a normal conversation then it "might" be considered as spamming. also the content of your message must be somehow related to the thread topic. to sum up, "it depends".

13. Whilst doing that, if your thread's first post is in massive font/spammed with loads of emotions, it will be locked/deleted and you may be warned.
So if you put tons it'll be locked.