Quoting Melanie Fetter:" To MammaNoodle: We took him to a eye dr and the show him cards that have a couple different colors on ... [snip!] ... very well. He can tell me yellow and orange pretty so that is a good start but I have to give him hints with the other ones."
hm... that's interesting. i would take him to his regular doctor (obviously just whenever you can get an appt--not an emergent situation), and tell him/her about it. i'd ask them who to take it to next. or, maybe ask at the preschool and see if they have a resource. as i said, it kind of seems like more of a cognitive thing (recognizing and understanding) if he is able to see color and speak the words.
so.... if you said 'green' to him, he could repeat it? and so on for the other colors beside orange and yellow? if he can say/repeat them, then obviously it's not a speech thing. so, i'd look into someone else. but i'm not exactly sure who that would be...