I'd say View of Collioure is like a classic plein air oil painting done in a different way. The colors are not realistic at all. They are much more vibrant and warm ---- the mountain in the background is straightforwardly pink with some strange green patches, the foreground is red, the walls of the houses are of various red and pink, the roofs are golden and red-orange, and the sea is too blue. It was painted very loosely. The brush strokes are evident and scattered. They were applied spontaneously and freely, almost like a crayon drawing. The artist didn't care to cover the whole surface of the canvas. Strokes, lines, and blocks of colors are often not adjacent right to each other, and the canvas shows through. However, the perspective is correct and creates a realistic depth of space. We can see very well that first there is the red foreground, then houses and wharves by the shore, then mountains across the water recede into the background. Matisse also put a short fat blue line in the upper right corner aside the distant mountain to indicate horizon line. Despite the strong and nonrepresentational colors, the rough brush strokes, the lack of details and light and shadow, the viewer can still get a pretty good sense that this image is about a real place. Maybe this painting was even done on site. I can imagine fishermen---or whoever---- living in the houses depicted in the painting. The bright warm colors make the image pleasant and inviting. It is a place you'd like to visit.
On the contrary, Factories at Horta de Ebro is not inviting at all. First of all, the buildings are reduced to basic geometric shapes. Some parts seem three dimensional yet perspectively wrong. The far end of the roof of the building to the left is