Adjectives ending with -ppoi

I recently read a new grammar form that I didn't know before, the word was 黒っぽい. Now I know that 黒い means black, but what about the 'ppoi' prefix, and how does that change the meaning to adjectives in general? And how does it work with na-adjectives?

Is the negative form 黒なっぽい? Is it also a correct usage?

Thanks for the answers. :)

kuroi (black) - kuroppoi (somewhat black)
shiroi (shiroi) - shiroppoi (somewhat white,, whitish)

If you want to say that something was not blackish, then it is "kuroppokunai." (Once "-ppoi" is added, because it ends in "i," it changes form as i-adjectives do, thus "kuroppokUNAI.")

With na-adjective or nouns + na/da:
kona (powder) - konappoi (powdery)
midori iro (green) - midori iroppoi

Not all adjectives can be expressed using this "-ppoi," as it has a sense of "somewhat...." or "vaguely...." I will post again if I can come up with certain guidelines for using this form :)

Haf,

Just to be pedantic, ''-ppoi'' is a suffix, not a prefix.
Secondly, it is added to nouns to make an adjective meaning ''looks/sounds/seems like (noun)''. Think of it as being similar to the way ''-ish'' or ''-y'' can be added to nouns in English to make adjectives, e.g. black - blackish or sugar - sugary.

You should treat it like any other ''-i'' adjective, so the negative form would be ''kuroppokunai'' and the past form would be ''kuroppokatta'' etc.

Nouns:
kodomo (child) - kodomoppoi (childish - in a negative sense)
otona (adults) - otonappoi (mature-looking)

At times it is used a bit more loosely to mean "somewhat..." or "it looks
like...":
dame (no good) - dameppoi (looks like it's going to be no good)

AND it CAN be used (mostly by young people - definitely not me :)) even with verbs, simply to blur or add the sense of "it looks like...":
okureru (verb, to be late) - okureruppoi (I think I'm going to be late!)

It's true, it is added to NOUNS ("kuro" is a noun for "the color black," the same with other color names as well) as Dave in Saitama says, that's a more accurate description :)

Aw man, I've been really slipping today. Fortunately it's weekend now. :)

Thanks you two. Of course it's a suffix and I don't even know why I added a -nai instead of the -kunai for adjectives. Guess I wass still sleeping in my bed when I wrote the question. ^^
Especially thank you for all the detailed information and the examples, they are very helpful! :)
I will try this form out on my japanese teacher as soon as she gets back from vacation. ^^