It is still not taking away the fact that the tricky cutting problem remains.
Ah, how can i solve the problem then?
Do away with the thin border bars. Try something else.
Or, just do away with them.
Your teacher is wrong.
You should be in CMYK mode.
Black is a colour.
It’s black pigment
White is not considered a colour as it’s without colour - you see the paper through the design.
White can be a colour - if printing in certain conditions, like packaging where it’s not a white background paper substrate.
I hadn’t noticed this earlier, but it’s wrong from so many angles that I’m unsure how to reply.
Picking up on what @Smurf2 said, color is your brain’s way of interpreting various wavelengths of light that strike the retina. From this viewpoint, black is the absence of visible wavelengths of light, and white is the combination of all the visible wavelengths.
In ordinary, everyday understanding, there’s a popular notion that neither black nor white are colors. But this is people’s misunderstanding of the relevant physics and biology that gives rise to color.
However, in graphic design and printing, color is more or less synonymous with how it’s produced using various combinations of inks, toners, dyes, pigments, electric diodes, etc.
In printing, if you want a specific color, you specify the appropriate combination of CMYK inks or a single Pantone color if the job calls for spot inks. Since black is the K ink in CMYK and has separate Pantone equivalents, black is undoubtedly a color in printing and graphic design.
White is usually the color of the substrate (the paper or whatever the inks are printed on). However, substrates aren’t always white. For example, the black background business cards you posted earlier could be printed with black ink on white paper stock. Alternatively, you could skip the black ink and use black paper stock and opaque white ink for the typography, as with white engraving ink or opaque thermography.
However, printing on black stock comes with problems since typical printing inks are transparent, but getting into that would be a digression.
You either misunderstood your instructor, or he or she is giving you incorrect information.
There’s another thing that every graphic designer needs to understand about color: CMYK (subtractive color) vs RGB (additive color). I’m skipping that for now since it would require another, even longer, post.