Lwisema, my translation (accepted) was "My dress is a red colour (no 's')" - this indicates that the speaker doesn't know what the name is for that particular shade of red (eg, vermilion, scarlet, crimson etc). It's just a red colour. Otherwise, the speaker would simply have said "My dress is red".
Your answer is just slightly off. You can't say logically "My dress is the colour red/green/orange", because the adjective is now describing the word "colour", not "My dress". You are saying your dress is a colour. It's not, it's a dress. The French sentence, having a colour, not being a colour, is more logical.
The English normally only use the phrase "the colour red/blue/pink" (with the adjective after the noun) in particular circumstances, eg "I love the colour red/blue/pink", ie, when talking specifically about the colour itself, not something that is that colour.
Putting the adjective before the noun, eg "It was a red colour", is perfectly acceptable, as in my answer at the start. But it requires "a" or "an", not "the". "The red colour" would only be used if you were choosing paint or material, for instance: "I like the red colour, not the yellow".
In my view, "My dress has a red colour" would never be said in English. Everyone knows red is a colour, therefore the extra noun "colour" is superfluous.
It's a very fine point, I know. Sorry for the long explanation.
No need to apologize. You are absolutely correct, the way one would say this in English is "My dress is the color red" omitting the work color if one feels like it.
This is one of the common problems with "machine translations". Things can "have a color" in English however the use of this phrase from a semantics p.o.v. is rather limited. Example: Does water have a color. Yes it is/can be blue. (you would not answer "it has the color blue".
If it were easy it wouldn't be English.
As a native speaker of English (U.S. variety) I would never say, "My dress has a red color." I think this is an exceptionally difficult phrase for translation. In English I might say, "My dress has a shade of red" or "My dress has some red in it" or "My dress is partly red" or "My dress is reddish."