<h3 dir="auto">Bug report</h3>
<p dir="auto"><strong>Bug summary</strong></p>
<p dir="auto">In 3.2, <code class="notranslate">scatter</code>  is color-mapping 4 points when the <code class="notranslate">c</code> input is 2D with shape (1, 4). This is a change from 3.1.</p>
<p dir="auto">The docs for <code class="notranslate">scatter</code> say</p>
<blockquote>
<p dir="auto">Note that <em>c</em> should not be a single numeric RGB or RGBA sequence<br>
because that is indistinguishable from an array of values to be<br>
colormapped. If you want to specify the same RGB or RGBA value for<br>
all points, use a 2-D array with a single row.  Otherwise, value-<br>
matching will have precedence in case of a size matching with <em>x</em><br>
and <em>y</em>.</p>
</blockquote>
<p dir="auto">However, this is no longer true.</p>
<p dir="auto">I suspect <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="606754505" data-permission-text="Title is private" data-url="https://github.com/matplotlib/matplotlib/issues/17245" data-hovercard-type="pull_request" data-hovercard-url="/matplotlib/matplotlib/pull/17245/hovercard" href="https://github.com/matplotlib/matplotlib/pull/17245">#17245</a> may be related (only based on milestone and description, I haven't debugged the code).</p>
<p dir="auto"><strong>Code for reproduction</strong></p>
<div class="highlight highlight-source-python notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="import matplotlib.pyplot as plt

x = y = 1, 2, 3, 4
c = [(.2, .5, .8, 1)]

f, ax = plt.subplots()
ax.scatter(x, y, c=c, s=100)  # Increase s for visibility"><pre class="notranslate"><span class="pl-k">import</span> <span class="pl-s1">matplotlib</span>.<span class="pl-s1">pyplot</span> <span class="pl-k">as</span> <span class="pl-s1">plt</span>

<span class="pl-s1">x</span> <span class="pl-c1">=</span> <span class="pl-s1">y</span> <span class="pl-c1">=</span> <span class="pl-c1">1</span>, <span class="pl-c1">2</span>, <span class="pl-c1">3</span>, <span class="pl-c1">4</span>
<span class="pl-s1">c</span> <span class="pl-c1">=</span> [(<span class="pl-c1">.2</span>, <span class="pl-c1">.5</span>, <span class="pl-c1">.8</span>, <span class="pl-c1">1</span>)]

<span class="pl-s1">f</span>, <span class="pl-s1">ax</span> <span class="pl-c1">=</span> <span class="pl-s1">plt</span>.<span class="pl-en">subplots</span>()
<span class="pl-s1">ax</span>.<span class="pl-en">scatter</span>(<span class="pl-s1">x</span>, <span class="pl-s1">y</span>, <span class="pl-s1">c</span><span class="pl-c1">=</span><span class="pl-s1">c</span>, <span class="pl-s1">s</span><span class="pl-c1">=</span><span class="pl-c1">100</span>)  <span class="pl-c"># Increase s for visibility</span></pre></div>
<p dir="auto"><strong>Actual outcome</strong></p>
<p dir="auto">On 3.2.1</p>
<p dir="auto"><a target="_blank" rel="noopener noreferrer nofollow" href="https://user-images.githubusercontent.com/315810/82120061-78059b80-9751-11ea-8f8f-8d73e34d9ea4.png"><img src="https://user-images.githubusercontent.com/315810/82120061-78059b80-9751-11ea-8f8f-8d73e34d9ea4.png" alt="image" style="max-width: 100%;"></a></p>
<p dir="auto"><strong>Expected outcome</strong></p>
<p dir="auto">On 3.1.2:</p>
<p dir="auto"><a target="_blank" rel="noopener noreferrer nofollow" href="https://user-images.githubusercontent.com/315810/82120042-57d5dc80-9751-11ea-8c68-073e82a8c896.png"><img src="https://user-images.githubusercontent.com/315810/82120042-57d5dc80-9751-11ea-8c68-073e82a8c896.png" alt="image" style="max-width: 100%;"></a></p>
<p dir="auto"><strong>Matplotlib version</strong></p>

<ul dir="auto">
<li>Operating system: macos</li>
<li>Matplotlib version: 3.2.1</li>
<li>Matplotlib backend (<code class="notranslate">print(matplotlib.get_backend())</code>): pylab inline</li>
<li>Python version: na</li>
<li>Jupyter version (if applicable): na</li>
<li>Other libraries: na</li>
</ul>
<h3 dir="auto">Bug report</h3>
<p dir="auto"><strong>Bug summary</strong></p>
<p dir="auto">Scatter <a href="https://matplotlib.org/3.2.1/api/_as_gen/matplotlib.axes.Axes.scatter.html?highlight=scatter#matplotlib.axes.Axes.scatter" rel="nofollow">docs</a> say that in order to provide a single RGB/RGBA color for all scatter elements, it is required to pass a 2D array with a single row for <code class="notranslate">c</code> argument input:</p>
<blockquote>
<p dir="auto">If you want to specify the same RGB or RGBA value for all points, use a 2-D array with a single row. Otherwise, value- matching will have precedence in case of a size matching with x and y.</p>
</blockquote>
<p dir="auto">When x/y shape is 3 and RGB is passed as a 2D array with a single row (e.g. <code class="notranslate">c=[[1, 0.5, 0.05]]</code>), or when x/y shape is 4 and RGBA is passed as a 2D array with a single row, the plot elements have several different colors (taken from the default colormap?) while all should have the same color. The problem occurs for both <code class="notranslate">plt.scatter</code> and <code class="notranslate">ax.scatter</code> calls, and also if <code class="notranslate">c</code> input is provided as a numpy array of shape (1,3) for RGB or (1,4) for RGBA instead of a nested list.</p>
<p dir="auto"><strong>Code for reproduction</strong></p>
<div class="highlight highlight-source-python notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="import matplotlib.pyplot as plt
plt.scatter(range(3), range(3), c=[[1, 0.5, 0.05]])
#alternatively, for RGBA scenario
plt.scatter(range(4), range(4), c=[[1, 0.5, 0.05, 1]])"><pre class="notranslate"><span class="pl-k">import</span> <span class="pl-s1">matplotlib</span>.<span class="pl-s1">pyplot</span> <span class="pl-k">as</span> <span class="pl-s1">plt</span>
<span class="pl-s1">plt</span>.<span class="pl-en">scatter</span>(<span class="pl-en">range</span>(<span class="pl-c1">3</span>), <span class="pl-en">range</span>(<span class="pl-c1">3</span>), <span class="pl-s1">c</span><span class="pl-c1">=</span>[[<span class="pl-c1">1</span>, <span class="pl-c1">0.5</span>, <span class="pl-c1">0.05</span>]])
<span class="pl-c">#alternatively, for RGBA scenario</span>
<span class="pl-s1">plt</span>.<span class="pl-en">scatter</span>(<span class="pl-en">range</span>(<span class="pl-c1">4</span>), <span class="pl-en">range</span>(<span class="pl-c1">4</span>), <span class="pl-s1">c</span><span class="pl-c1">=</span>[[<span class="pl-c1">1</span>, <span class="pl-c1">0.5</span>, <span class="pl-c1">0.05</span>, <span class="pl-c1">1</span>]])</pre></div>
<p dir="auto"><strong>Actual outcome</strong><br>
<a target="_blank" rel="noopener noreferrer nofollow" href="https://user-images.githubusercontent.com/13831112/82084053-5d043e80-96f3-11ea-9d01-5b8afa216e0a.png"><img src="https://user-images.githubusercontent.com/13831112/82084053-5d043e80-96f3-11ea-9d01-5b8afa216e0a.png" alt="840-mpl" style="max-width: 100%;"></a></p>
<p dir="auto"><strong>Expected outcome</strong><br>
All points have the same color: RGB (1, 0.5, 0.05).</p>
<p dir="auto"><strong>Matplotlib version</strong></p>

<ul dir="auto">
<li>Operating system: Linux</li>
<li>Matplotlib version: 3.2.1</li>
<li>Matplotlib backend (<code class="notranslate">print(matplotlib.get_backend())</code>): agg</li>
<li>Python version: 3.7.3</li>
</ul>


<p dir="auto">Matplotlib installed through pip</p>