RGB, LAB, HSV and many others are colour spaces, that is how to create colours that resemble what natural colours are, see for instance
Images from cameras will come as RGB in most cases, that means that every pixel has 3 values for the intensities of Red, Green and Blue channels. These will be different from LAB or any other colour space.
How can I display these values ?
Well, if you want to visualise as an image, then use imagesc or imshow where the three values will be interpreted as colour. You may want to visualise them separately as
You may want to view the values so just type a range in the command window
do not use semicolon in the end to echo to the screen the values.
Should I find RGB value of the location first and then convert it into LAB color space, or is there any other way?
you can convert the whole image in a single command:
your_image_LAB = rgb2lab(your_image);
Hope this helps. If this solves the problem, please accept the answer, if not, let me know.