All fields require one space between them and the next field.

This position is used for the attribute byte. So a +1 in DDS will insure that it compiles, whereas an RPG output spec-style +0 will never compile.

There are times when you need two spaces between fields. 

A field with CNTFLD keyword specified needs two spaces before it in order for it to function properly.  There are also other keywords that require two spaces, like SNGCHCFLD and MLTCHCFLD..

And there is no difference between color and monochrome; just changes how it's rendered.

• There's a leading (invisible) attribute byte before each field.
• There's a trailing (invisible) attribute after each field.
• Between two fields the attribute can be shared. You need a minimum of one (invisible) space for the shared attribute byte. I.e., the leading attribute of the 2nd field also acts as the trailing attribute of the first field.
• Be aware that fields wrap from line to line. If a field ends in column 80, it's trailing attribute is in column 1 of the next row. The next field can't begin before column 2. Not 100% sure, but I believe there's also a wrap from 24,80 to 1,1. (Or 27,132 to 1,1 if you're *DS4.)

 Plus what Fisher said.

Yes, position (1,1) on the display cannot be written to. It is blocked. But a field's attribute may appear there.