Why do images with CMYK color mode don't show up on the Web?

Question

And for tshirt printing, what will I use: CMYK or RGB?

Answer 1

Regarding your first question, it is that computer monitors only display in RGB mode, so, ALL display colors have to work within that gamut.  There are, more limited color gamuts, such as the 256 colors of the GIF format, but, even these fit withing the RGB color gamut.

As far as printing, you can't mix RGB colors in pigment.  For instance, how would you get yellow out of those three colors?  Or purple?  Or Orange.  In a computer screen, you can, because on screen, colors are mixed by REMOVING colors instead of adding them.

Answer 2

The Internet does not use CMYK. You will need to add colors using either RGB or HEX values. I've shared a really good color converter website that I use below.

For printing T-shirts, silk screeners use the four color process (CMYK). If your designs have 1, 2 or perhaps 3 colors, then you can use pantone colors.