He wore a sky-piercing crown and donned a robe of ochre-yellow.

The 沖天冠, the "sky-piercing" cap, was the sovereign's; 冠 here is the noun, guān. The 赭黃袍, ochre-yellow robe, was reserved to the emperor by law — wearing that particular colour was a capital offence for anyone else.

He fastened a belt of Lantian green jade and trod in a pair of 'founding, care-free' boots.

藍田碧玉 is the celebrated green jade of Lantian in Shaanxi, the finest in China. And then the boots: 創業無憂履, "founding-the-enterprise, free-of-care" boots. Chinese court dress ran to auspicious names, and these ones are effectively a slogan worn on the feet. 繫 is xì, to fasten.

His countenance imposing, surpassing the courts of the age;

賽過當朝 is to outshine the present age; 朝 is cháo.

his majesty blazing, flourishing anew this very day.

重興, chóng xīng, is to flourish again — 重 as chóng, "once more," not zhòng, "heavy," and 興 as xīng, to rise. Both words are doing double duty: the reign flourishes again, and so does the man.

What a Tang king, ruling in peace and virtue! What a Lord Li, risen from death to life!

清平有道, "peaceful and possessed of the Way," is the formula for a good reign. And 起死回生 — "raise the dead, return to life" — is still the everyday Chinese superlative for a doctor or a rescue: to bring someone back from the brink. Here, for once, it is meant literally.