enigmatic puzzle - Rainbow Road Rabbit Hole

Question: Who is in first place?

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It's difficult to add hints in the puzzle itself given its nature so I'll try to add some notes here as text instead.

Red: [Solved]

Orange: [Solved]

Yellow:

K1

Answer

This puzzle is rainbow (road)-themed, and consists of a series of colored images. Each image contains the URL of the next image, encoded or obfuscated in some fashion.

Steve Eckert started us off by solving the "red" and "orange" images.

The "red" image (the image in the OP) used a traditional steganographic technique:

the URL was hidden in plain text, in a color one bit different from the background.

The "orange" image uses a classic encoding method:

The URL is encoded as Morse code.

f'' was next to step in, solving the "yellow" image:

The URL was enciphered using the same Vigenere cipher as the famous Kryptos sculpture whose coordinates were in the image.

This revealed the "green" image:

http://i.stack.imgur.com/b8qwn.png

This image contains a number of barcodes. Each of the barcodes on the first row encodes a single character from the URL:

The first is an Aztec code. Using Mathematica to decode it produced m. (I verified its contents by hand, since I've been working a lot with 2d barcode formats in preparation for my next puzzle.)

The second is a Code 128 barcode, containing the letter L. I used Mathematica to decode this one as well.

The third and fifth are Code 39 barcodes, containing +C and W. The former is actually using the full ASCII extension to code a lowercase c. I decoded these by hand using the picture on the Wikipedia page.

The last large barcode is a MaxiCode, used mainly by UPS. This was by far the most difficult part of the puzzle, since it's hard to find information on the format, and there aren't any online MaxiCode readers (since nobody except UPS needs to read the barcodes, only generate them). I eventually installed a trial version of some computer vision software to reveal that the barcode contained only .png. (It was obvious in retrospect that the repeated pattern in the upper half of the barcode is just padding in the outer data area, since the barcode is a fixed size.)

This gives us all but one of the characters in the URL. Brute-forcing the remaining character by programmatically trying all 62 possible characters leads us to the "blue" image:

http://i.stack.imgur.com/mLc1W.png

We can see the letters p, n, and g on the right, so it's apparent that we must rearrange the letters using the values on the left in order to retrieve the next URL.

I'm too impatient to figure out what $B'_L$ and $\beta$ are, so I programmatically searched all 120 permutations of the right-hand side that ended in .png, leading to the "magneta" image:

http://i.stack.imgur.com/xfrqT.png

The solution seems to indicate that we were supposed to order the left-hand side by value, so we know that $\beta < B'_L < \sqrt{2}$. It could be that $B'_L$ is supposed to be Legendre's constant, $1$, in which case $\beta < 1$ (but I still don't know what $\beta$ is; oh well).

The next URL is encoded with a simple

Caesar cipher, which I figured out by noticing the difference between c and a was the same as the difference between p and n (what I would expect to be in the plaintext there). (As Zandar points out, this particular Caesar cipher is rot13, with to "rot5" for the numbers.)

Using a known-plaintext attack on the extension (.png), we get:

http://i.stack.imgur.com/T*gf*.png

I wasn't sure how the cipher was supposed to affect the digits, so I once again brute-force searched all 100 possible digit assignments, which turns up (along with two false positives) the "purple" image:

http://i.stack.imgur.com/T1gf2.png

You can tell that we're dealing with a transposition cipher, since all the characters from the expected URL format (http://i.stack.imgur.com/*.png) are here. Playing around some reveals that it's a simple

transposition cipher with 12 columns.

Note that in order to decode it correctly, some of the spaces in the text have to be doubled or trebled. With the correct spacing, I get:

Y       s i a t . i o 9
o a t H   n g t s m m .
u l h e t a e p t g / j
  m e r h l : : a u 5 p
a o r e e     / c r Y g
r s e     i   / k . 8
e t . i f m h i . c u 

or:

You are almost there. Here is the final image: http://i.stack.imgur.com/5Y8u9.jpg

Yielding the final part of the puzzle:

http://i.stack.imgur.com/5Y8u9.jpg

In the spirit of the challenge, I'll present the answer as an image of my own: