What was the first widescreen film in color? Song of the Flame doesn’t count, because part of that film was in black and white, and part of the film was also non-widescreen. And hand-colored films don’t count either, because the films were shot in black and white.
“Fred Ott’s Cylindrographe Success in Unblushing Color!” Looking for an ad like that? Your question, like that in the Find A Grave forum “The Lounge” is vague enough to encourage various answers. And assuming that there is no hurry, I posit that no one can give a definite answer. A stimulating question, though…
[ul][li]“Nobody knows what the first color movie was…Color movies date back to the 1890s…”, per http://www.widescreenmuseum.com/oldcolor/.[/ul][/li][ul][li]Sometime during 1894-1896 someone filmed the Henley Regatta in widescreen. Herman Casler built the special projector, per http://www.in70mm.com/news/2010/widescreen/.[/ul][/li][ul][li]In 1899, Edward Raymond Turner patented a color film process. Around 1901-1902 he filmed some color movies, which were successfully shown for the first time in 2012, if I correctly understand Gizmodo here. The images look slightly wider than square. [/ul][/li]Here’s hoping that someone finds the actual answer in our lifetime.
A more pedestrian but accurate answer is that Becky Sharp was the first feature length film released in Technicolor. Aside from the horrific aspect ratios created by cellular phones ( which can be shot in Portrait aspect instead of Landscape ), ALL films released from the 1890’s forward are wide screen.
Were you looking for the first feature film shot in 1.85:1 Academy spherical aspect ratio that was color? The first feature film shot in Cinemascope ( 2.66:1 ) that was color?
Likely you’re going to get a LOT of answers to this one till you narrow the parameters down a wee bit. 
With those limitations, and adding to that a commercially released film, either This Is Cinerama (although that had a prologue that was neither colour nor widescreen, and was basically a tech demo), or either The Robeor How To Marry A Millionaire, depending whether you count release date or production date.
This may seem later that you’d expect, but the early widescreen processes had been abandoned by the time full colour processes were available for practical use. There may well, as from a_to_z says, have been some small scale experiments prior to 1930, but no major films.
Academy Ratio is 1.375:1. 1:85.1 is widescreen, as that term is normally used.
I downloaded the first part of This is Cinerama, including the prologue, and put it on YouTube, because I wasn’t able to hear it prior to me putting it on YouTube: http://www.youtube.com/watch?v=ULBdcC9jSGQ
So I saw the black and white prologue to it, which now brings me to my next question:
If the prologue is in B&W, is it correct to say that This is Cinerama is a part color/part B&W film, or is it correct to say that This is Cinerama is an all-color film and pretend the prologue doesn’t exist, since it’s just a prologue?
I would say that This is Cinerama is part-color, part-B&W. The prologue is an integral part of the film.
Here’s some valuable information on the transition to widescreen during 1953:
http://www.3dfilmarchive.com/home/widescreen-documentation
Becky Sharp was the first feature shot entirely in the 3-strip Technicolor process. The absolute first Technicolor feature was The Gulf Between, which was screened privately in September 1917 and released in February 1918. It was the only movie to use Technicolor’s 2-color additive system. The more successful 2-color subtractive process debuted with The Toll of the Sea in November 1922.
As an avid fan of amateur filmmaking who’s used widescreen processes, I would be qualified to answer this question. In the 1950s, anamorphic widescreen was the only technique in the world available for the general public to use to make widescreen movies, because all widescreen films were anamorphic widescreen films. The first widescreen film was “Construire un Feu”. The next four widescreen films were “Une Visite aux Merveilles de l’Exposition Coloniale Internationale”, "La Femme et le Rossignol ", “Phenomenes Electriques”, and “Panoramas au fil de l’Eau”. The fifth widescreen movie was also the first widescreen film in color: “The Robe” (Actually, “Phenomenes Electriques” was in color too, but it was a cartoon, so it doesn’t count.).
Dangit I should know this because I wrote a thesis paper about it in college: unfortunately that was 20 years ago. I do remember the first film in VistaVision was “White Christmas”. But it wasn’t the first widescreen; it was a “response” to CinemaScope.
I stand corrected.
I wuz gonna make a guess. But this forum kind of sucks to play this game because by the time I want to post my guess, someone already posted the winner and the only way I can tell this is if I read every post.
The format of this forum just does not lend itself to playing this kind of game.
Sorry.
OMG! You’re so right. There were nine - that’s 9! - whole posts between yours and the OP’s. That much reading can sprain your brain! You’re really better off avoiding doing work of such depressing magnitude and then going through all the effort to post it. So are we, for that matter.