How do i determine the pixel coordinates of an image using RGB values?

For example: i'd like to get the coordinates of the pixels with R values from 230 to 250.

Answer 1

[JESUS DAVID ARIZA ROYETH]

image=imread('peppers.png');
R=image(:,:,1);%red chanel 
[x,y]=find(and(R>=230,R<=250));%here coordinates