Lazy, Firm or Rebellious?

When I went to pick up Lucas from school today, the teacher told me Lucas did not want to do his school work. I sensed something was amissed earlier. After their Good-Bye song, the teacher had a rather long chat with him. I was wondering if he made a fuss earlier and the teacher had to pacify him. When the teacher told me what happened, I was rather surprised. So, I told myself I need to get to the bottom of this matter. Asking him in school will be a waste of time. He will not want to talk about it. So, after we came home and had his lunch and bath, I subtly asked why he did not want to do his work in school. He said 'I do not want to be busy'. Ok...I let it go and will ask more later - one question at a time. If he doesn't want to talk about it, he will not say a word. If he wants to talk about it, he will spill all the beans - whether you asked for it or not.
At night, after I read him his bedtime story, he was very chatty. I took the opportunity to ask again. This time, he said 'I do not want to use 4 colours to paint the heart shape. It is too much'. Ok...so it sounded like he does not agreed to use 4 colours to paint the heart shape picture. Therefore his action of not wanting to do his work.

It is not the end yet. Tomorrow I will ask him what's wrong with using 4 colours? Can't he use whatever colours he wants? Will also tell him to tell his teacher if he doesn't agree. After that??? Tell him to stand firm by his opinion or just follow teacher's instruction?