Incomplete color wheel - one color not allowed

Is the answer the following?

Any Hue (city in Vietnam) of purple is forbidden (from Forbidden Purple City, a UNESCO World Heritage Site within Hue).

Explanation:

Reading counterclockwise, starting immediately after the white section, we have the following RGB colours (? for the unknown colour):

(102, 255, 229)
(102, 179, 255)
(255, 127, 102)
(102, 255, 153)
(229, 255, 102)
(102, 204, 255)
(102, 255, 255)
(179, 255, 102)
?
(255, 204, 102)
(255, 127, 102)
(102, 255, 153)
(255, 127, 102)
(102, 255, 153)
(229, 255, 102)

Taking the hue of each colour (and rounding to the nearest integer) gives

170
210
10
140
70
200
180
90
?
40
10
140
10
140
70

Now notice that these are all divisible by 10.

170 -> 17
210 -> 21
10  -> 1
140 -> 14
70  -> 7
200 -> 20
180 -> 18
90  -> 9
?   -> ?
40  -> 4
10  -> 1
140 -> 14
10  -> 1
140 -> 14
70  -> 7

These numbers are all less than 26, so maybe they represent characters (A = 1, B = 2, C = 3, ..., Z = 26). Let's try:

17 -> Q
21 -> U
1  -> A
14 -> N
7  -> G
20 -> T
18 -> R
9  -> I
?  -> ?
4  -> D
1  -> A
14 -> N
1  -> A
14 -> N
7  -> G

We get the string "QUANGTRI?DANANG"
We would like to know what's between "QUANGTRI" and "DANANG".

The answer is the name of a thematic region and a landmark within it that is being rebuilt.

Quang Tri is a Vietnamese province, and Danang is a Vietnamese city. What's between them? A quick search shows that the Vietnamese city of Hue is geographically sandwiched between them. Furthermore, a UNESCO World Heritage Site within Hue is called the "Forbidden Purple City".

The black section below cannot be a certain color.

Given the name "Forbidden Purple City", I would suppose that purple is the forbidden colour.

To find the colours, I used an online colour picker. To do the deciphering, I wrote this Python script:

cols = [
    (102, 255, 229),
    (102, 179, 255),
    (255, 127, 102),
    (102, 255, 153),
    (229, 255, 102),
    (102, 204, 255),
    (102, 255, 255),
    (179, 255, 102),
    (255, 204, 102),
    (255, 127, 102),
    (102, 255, 153),
    (255, 127, 102),
    (102, 255, 153),
    (229, 255, 102)
]

def hue(r, g, b):
    r, g, b = r / 255.0, g / 255.0, b / 255.0
    mx = max(r, g, b)
    mn = min(r, g, b)
    df = mx - mn
    if mx == mn:
        h = 0
    elif mx == r:
        h = (60 * ((g - b) / df) + 360) % 360
    elif mx == g:
        h = (60 * ((b - r) / df) + 120) % 360
    elif mx == b:
        h = (60 * ((r - g) / df) + 240) % 360
    return h

abc = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
for c in cols:
    i = int(int(round(hue(*c)))/10)
    print(abc[i-1], i)