The possuk after the avoda of Yom Kippur says, ’Vayaas kaasher tzeiva Hashem es Moshe‘. Rashi explains this posuk implies praise of Aharon that he did not wear the clothes of kahuna for his own greatness but rather to do the mitzvah of Hashem.

On Yom Kippur he only wore four of the eight clothes, the white ones and not the gold. Doesn’t this indicate less respect for Yom Kippur by not wearing the gold?

The Chassam Sofer explains that it would be an embarrassment for Aharon to go into the Holy of Holies with golden clothes because it would remind Hashem of the sin of the golden calf. Therefore Aharon should be happy not to wear the golden clothes. However, he really would have been happy to wear the gold in spite of the embarrassment, if that would have caused atonement for Klal Yisroel. Still, he wore the white because that is what Hashem said and for that he is praised.