Output only some frames

I'm using a depth camera and am wanting to know if there is a way to only output frames where the object is close enough here is part of the code where the depth is transformed into RGB

% Select depth frame

depth = fs.get_depth_frame();

% Colorize depth frame

color = colorizer.colorize(depth);

% Get actual data and convert into a format imshow can use

% (Color data arrives as [R, G, B, R, G, B, ...] vector)

data = color.get_data();

img = permute(reshape(data',[3,color.get_width(),color.get_height()]),[3 2 1]);

What kind of if function could I input after this where I would only output frames with a certian percentage of blue in the frame (when object is within certian distance)

[Walter Roberson]

rgb2hsv and select pixels with appropriate range of Hue, in order to categorize as blue? mean() of the logical array would be fraction occupied