For the majority of people, Social Security Disability benefits are not taxable. This is true for people who have income in addition to disability benefits as well as those who do not. (Most of the one-third of disability recipients who do pay taxes on benefits receive SSDI benefits, not SSI.
Mixing all three gives black. The CMYK color model (process color, four color) is a subtractive color model, used in color printing, and is also used to describe the printing process itself. CMYK refers to the four inks used in some color printing: cyan, magenta, yellow, and key (black).
The underlying color model in Photoshop is neither RGB nor CMYK but LAB. It has the widest gamut, which means it can hold more color values than any other model. Of the two other models, RGB has more color values than CMYK does. When you convert from RGB to CMYK, the program first maps the RGB values into the LAB colorspace. It then maps the LAB values into the CMYK colorspace. Now, for REAL entertainment...take a pure RGB blue, or a pure RGB green, and attempt to map it into CMYK colorspace. It doesn't work at all.