Is there a thing in my mind? Is that how it's phrased? I understand there is the definition of apple as a concept...is this what is in my mind? The definition doesn't include red though...Honestly I would have said that if there is a thing and I'm thinking about it, there are two different entities, there is the real thing that exists and there is the concept of it in my mind, but this doesn't seem to be correct. Can anyone please tell me what actually is in my mind? Is it called a concept? Thanking you in advance.
According to representationalism, which is probably the most popular philosophical approach to perception these days, when you perceive a red apple, you token a representation of the apple. This representation, which is the percept itself or a related entity, represents the apple, in the sense that it will typically have accuracy conditions that are sensitive to the apple---say, the representation will be false, or inaccurate, if it represents the apple as red but it is green.
Now, many, although by no means all, philosophers will say that perceptual representations are non-conceptual: they are not constituted by concepts, at least if concepts are taken to be the same entities we think and judge with. Perceptual representations earn their accuracy conditions in some other way, perhaps simply by tracking extramental states of affairs.
In any event, you are perfectly right: when you think of, or perceive, an existing red apple, there are two things: a mental state of yours that represents the apple, and the apple out there. Only the latter is red; the formerly merely represents the apple as being red.