I’m the color of warning and warmth, of ripened fields and rising suns. I shine without being gold. What am I?

I speak in pairs but never make a sound, Write a lifetime without pen or ground. Four symbols bind, yet none are seen, I copy myself to stay in-routine.

A calm comes before me. Sometimes, I am evil enough to scare dogs when I approach, and yet, sometimes kind enough to bring great relaxation to you.

When Phoebus slow doth dip his golden crown, The sky's canvas blushes in hues of renown. Day's final breath, ere night takes her throne, A radiant farewell, where dreams are sown.

I guard the fields with a prickly stare, Purple crowns upon my hair. Ignored by hands, yet bold and brave, I flourish where the wild things wave. Touch me wrong and you’ll soon see- What thorny symbol could I be? Want it harder, shorter, or with a mythicalhsymbolic twist?