Based on the sequence of rectangles you see below, which rectangle (A-E) should replace the question mark? Once you figure out what this puzzle is all about you'll know which of the five should replace it.

Six sets of three rectangles each, partly coloured in, followed by a question mark, then five sets of three rectangles labelled A-E

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    $\begingroup$ Just want to add; the knowledge required is basic and something you're all most likely familiar with. So, no need to search all over the internet to find something that "fits." You just have to make sense of it somehow and use google (where it's needed) to confirm your findings. $\endgroup$ May 8, 2023 at 10:51

1 Answer 1


This puzzle is all about

Rectangles Gone Black, or RGB for short! And the missing rectangle is B.

There are a total of

7 sets of three-box-triplets, matching the number of colors in the rainbow; so it makes sense to treat the sets as RGB values for the respective colors.
The colors have 'gone black' in the sense that instead of (255,0,0) for red (using the first rectangle as an example), three boxes are used: {100% fill, 0% fill, 0% fill} where the fill % is based on the individual value from 0-255.
- R - G - B

The first box, red, is RGB(255,0,0), so it shows 100%,0%,0%.
Orange could be RGB(255,155,0), so it could show 100%, 61%, 0%. Actually box 2 shows 50%, but that's just another shade of orange (255,128,0).
Yellow is RGB(255,255,0), so it shows 100%, 100%, 0%.
Green and blue are easy; the respective boxes are at 100%.
Using 25%, 0%, 50% gives the named web color indigo, more of a purplish hue than traditional indigo.
Based on how indigo was treated, I'll assume we are looking for box 7 to contain the named web color violet. Violet is RGB(155,38,182), or 60%,15%,71%. Box B is the closest match, so this shade of Violet is our answer!
By the way, here's a picture of Rectangle B. If you calculate the other boxes, they do not at all look like 'violet'.

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    $\begingroup$ This is it! That's the correct answer. Was planning to give a hint regarding the title. Nice catch and great job! $\endgroup$ May 9, 2023 at 8:24

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