According to The Longman Student Grammar of English (Biber et al., 2002 Pearson Education ESL), “orthographic words” are words
that we are familiar with in written language, where they are separated by spaces
The authors then give an example:
They wrote us a letter.
which contains five orthographic words.
What about words that have the same meaning yet different spelling? Are the examples provided in the title of this question, color and colour, therefore two different orthographic words?