ofVec3f the closest value in the array

Hello guys,

maybe someone can help me!
I built a struct like this:

struct{
   char id;
   ofVec3f rgb;
}Colors;

I create an array of struct with 255 elements:

Colors col[255];

populated the array of struct like this:

 colors[0].id='\x00'; colors[0].rgb=ofVec3f(0,0,0);
 colors[1].id='\x01'; colors[1].rgb=ofVec3f(0,0,0);
 colors[2].id='\x02'; colors[2].rgb=ofVec3f(0,168,0);
 colors[3].id='\x03'; colors[3].rgb=ofVec3f(0,168,0);
 colors[4].id='\x04'; colors[4].rgb=ofVec3f(168,0,168);
 colors[5].id='\x05'; colors[5].rgb=ofVec3f(168,0,168);
 .....

I have a function that makes a loop on the array "struct Colors" and takes as input a ofVec3f:

char update(ofVec3f col) {
        char id;
        for (int i = 0; i < NUM_CHART_MAP; i++) {
          ofVec3f rgb = colors[i].rgb;
          if(rgb == col) {                          <------------------------------- this if() is wrong!
               id=colors[i].id;
          }
        }
        return id;
}

I want to find within the array of struct the value nearest to ofVec3f input.

excuse me English, I hope I explained.

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