子夏 was Confucius student. After Confucius's death, he was teaching Confucius ideas to people and had huge influence at his time.
The first 賢 in 賢賢易色 is used as a verb meaning "getting close to 賢". The second 賢 is used as a noun meaning "people of good character and quality". 易 is "change" and 色 is "colour". That this sentence means is that when one get close to a person with good character and quality, one will recognize and change one's attitude towards that person.
父 is "father" and 母 is "mother". Together, 父母 means "parents".
When serving one parents, one would use all the energy
君 is used as "friend" here - a friend who you know well.
When helping a friend, one would commit oneself completely.
When with friends, one's words are trustworthy.
Anyone, who can do the above three things, although you may say s/he has not gone to school, I would say s/he is a learnt person.
Again, this paragraph shows what Confucius considered as learning - to learn to become a good person.