Flexive morphemes are those used to make plurals (-s), set the gender of the word (-o, -a), or conjugate verbs (as in cant-aré). Strictly speaking, a word than admits a plural but is in singular form, has an empty flexive morpheme at the end, see here:
- cosa -Ø (singular)
- cosa -s (plural)
Derivative morphemes change the meaning of the word, such as -idad in "activ -idad", which transforms the adjective "activo" into a noun.
Let us take a look at your examples. All derivative morphemes are highlighted in bold, and all flexive morphemes in italics:
person -al (-Ø)
Here, -al is a derivative morpheme. This is a tricky case, as "personal" might be an adjective meaning "personal" in English (in which case it has an empty flexive morpheme at the end because it admits a plural form) or it can be a noun meaning "staff" in English, in which case it has no flexive morpheme because it does not admit a plural.
verd -os -o -Ø
Here, -os is a derivative morpheme, which changes the meaning of "verde". The morpheme -o is flexive, because it sets the word as masculine. Similarly, there is an empty flexive morpheme at the end because the word is in singular form.
Here, -idad is a derivative morpheme, which changes the meaning of "legal". There are no flexive morphemes, because (as far as I know) "legalidad" has no plural form.
des- cortés -Ø
Here, des- is a derivative morpheme, and there is an empty flexive morpheme at the end because the word admits a plural form.
As you have seen in the examples, derivative and flexive morphemes often appear together in a word.