To see red - feel angry
To feel blue - to feel sad
To be green - young or inexperienced
to be in a black mood - to be grumpy and irritable
Someone who is yellow is a coward
the sound of a bell can be described as silver
You can probably think of lots more examples of mingling the senses with language.
Just for fun I'll try and think of a few sentences,
The silver sound of the sparkling stream
Woke me from my perfumed dream
Of beautiful pine trees caressed by the sun
Stroking the sky and blowing the clouds
While we lay beneath them, as one
So that is synaesthesia in a nutshell.
Here is a link to one of my favourite songs to cheer you up, ready for Monday, guaranteed.
I don't care if Monday's blue
Tuesday's grey and Wednesday too,
Thursday I don't care about you
Cos Friday I'm in love ...