Do you think that little blue thing satisfactorily expresses the sentiment?
Um...no? Yes? Is this a trick question? 

I always associate blue emojis with sad stuff. There is disonance . . .
Could that be because in the English language one can 'feel blue'? In Portuguese, we do not suffer from such hues. 
So you can't sing the bluese in Portuguese?
Nope, blue is not associated with sadness as far as I know. But it's likely it'll be an imported and incorporated expression in the future. For now, it's the colour you get when you're
starving ("blue from hunger").
Can you Portuguese speakers go white with fear or anger?
White with fear or anger, yes.
Green with envy?
This is believed to have originated with Shakespeare himself. It's not very common, but because his works are read here, the expression has been incorporated. Some people say it.
Yellow in cowardice?
Yes, 'to go yellow' (amarelar) means to, well, go
yellow.
Into a black rage?
Never heard an equivalent before.

There is a popular expression with
black in it, but it's used to mean something has gone wrong or has become complicated.
Pink or red with embarrassment?
Purple.
Or even transparent if totally ingenuous?
Not really, someone who isn't hiding anything is transparent.