I can confirm this bug. Some more details:

1. It is also present with xf86-video-ati

2. When I compile it with the following autogen flags, the issue is not present: --prefix=/opt/xorg --enable-glamor --with-xkb-path=/usr/share/X11/xkb --enable-config-udev

3. I use Ubuntu 16.04, so I downloaded the deb source and found the autogen flags that are used for the official deb package, and they are as follows:

--build=x86_64-linux-gnu lt_cv_prog_compiler_static_works=no --disable-silent-rules --disable-static --without-dtrace --disable-strict-compilation --disable-debug --enable-unit-tests --with-int10=x86emu --with-extra-module-dir="/usr/lib/x86_64-linux-gnu/xorg/extra-modules,/usr/lib/xorg/extra-modules" --with-os-vendor="Ubuntu" --with-builderstring="xorg-server 2:1.18.2-1ubuntu0.2 (For technical support please see http://www.ubuntu.com/support)" --with-xkb-path=/usr/share/X11/xkb --with-xkb-output=/var/lib/xkb --with-shared-memory-dir=/dev/shm --enable-mitshm --enable-xres --disable-xcsecurity --disable-tslib --enable-dbe --disable-xf86bigfont --enable-dpms --enable-xshmfence --disable-config-hal --enable-config-udev --enable-xorg --disable-linux-acpi --disable-linux-apm --disable-xquartz --disable-xwin --disable-xfake --disable-xfbdev --disable-install-setuid --with-default-font-path="/usr/share/fonts/X11/misc,/usr/share/fonts/X11/cyrillic,/usr/share/fonts/X11/100dpi/:unscaled,/usr/share/fonts/X11/75dpi/:unscaled,/usr/share/fonts/X11/Type1,/usr/share/fonts/X11/100dpi,/usr/share/fonts/X11/75dpi,built-ins" --enable-aiglx --enable-composite --enable-record --enable-xv --enable-xvmc --enable-dga --enable-screensaver --enable-xdmcp --enable-xdm-auth-1 --enable-glx --enable-dri --enable-dri2 --enable-glamor --enable-dri3 --enable-libdrm --enable-present --enable-xinerama --enable-xf86vidmode --enable-xace --enable-xselinux --enable-xfree86-utils --enable-xwayland --enable-systemd-logind --with-systemd-daemon --enable-suid-wrapper --enable-dmx --enable-xvfb --enable-xnest --enable-kdrive --enable-xephyr --enable-xmir --with-sha1=libgcrypt --enable-xcsecurity

4. I rebuilt from git using the following flags (slight modification of the above flags), and was able to reproduce the bug:

--prefix=/opt/xorg --build=x86_64-linux-gnu lt_cv_prog_compiler_static_works=no --disable-silent-rules --disable-static --without-dtrace --disable-strict-compilation --disable-debug --with-int10=x86emu --with-xkb-path=/usr/share/X11/xkb --with-xkb-output=/var/lib/xkb --with-shared-memory-dir=/dev/shm --enable-mitshm --enable-xres --disable-xcsecurity --disable-tslib --enable-dbe --disable-xf86bigfont --enable-dpms --enable-xshmfence --disable-config-hal --enable-config-udev --enable-xorg --disable-linux-acpi --disable-linux-apm --disable-xquartz --disable-xwin --disable-xfake --disable-xfbdev --disable-install-setuid --with-default-font-path="/usr/share/fonts/X11/misc,/usr/share/fonts/X11/cyrillic,/usr/share/fonts/X11/100dpi/:unscaled,/usr/share/fonts/X11/75dpi/:unscaled,/usr/share/fonts/X11/Type1,/usr/share/fonts/X11/100dpi,/usr/share/fonts/X11/75dpi,built-ins" --enable-aiglx --enable-composite --enable-record --enable-xv --enable-xvmc --enable-dga --enable-screensaver --enable-xdmcp --enable-xdm-auth-1 --enable-glx --enable-dri --enable-dri2 --enable-glamor --enable-dri3 --enable-libdrm --enable-present --enable-xinerama --enable-xf86vidmode --enable-xace --enable-xselinux --enable-xfree86-utils --enable-xwayland --enable-systemd-logind --with-systemd-daemon --enable-suid-wrapper --enable-dmx --enable-xvfb --enable-xnest --enable-kdrive --enable-xephyr --with-sha1=libgcrypt --enable-xcsecurity

5. I ran a git bisect after building with the flags from #4, and found the bad commit:

# first bad commit: [0cd5b9525a8f661c6b2545c21ce1ba21577c009e] glamor: Use GL_RED instead of GL_ALPHA if we have texture_swizzle (v3)

Link to the commit: https://cgit.freedesktop.org/xorg/xserver/commit/?id=e6754dcb59ee21abb42421a28f4e467295584f67

fix committed to master

commit a288cf58a0dc0f965a6f964c76bb86bb1989d797
Author: Dave Airlie <airlied@redhat.com>
Date:   Wed Mar 16 10:45:54 2016 +1000

    glamor: swizzle RED to 0 for alpha textures

I applied https://cgit.freedesktop.org/xorg/xserver/commit/?id=a288cf58a0dc0f965a6f964c76bb86bb19  on 1.18.2

I still experience this red colour bug on feedly

In youtube html5 player, youtube chat text etc
its all reddish text.

Also in some svg icons for owncloud like this one; it renders red, it should be black.

https://github.com/owncloud/core/blob/master/core/img/places/home.svg

(In reply to Bug from comment #3)
> I applied
> https://cgit.freedesktop.org/xorg/xserver/commit/
> ?id=a288cf58a0dc0f965a6f964c76bb86bb19  on 1.18.2
> 
> I still experience this red colour bug on feedly
> 
> In youtube html5 player, youtube chat text etc
> its all reddish text.
> 
> Also in some svg icons for owncloud like this one; it renders red, it should
> be black.
> 
> https://github.com/owncloud/core/blob/master/core/img/places/home.svg


 Driver "radeon"
 Identifier "4760"
 Option "AccelMethod" "glamor" 
 Option "DRI" "3"
 Option "TearFree" "1"


mesa 4e060d80ff92b7fcf9b54cdd5ed00f549db3f573  Date:   Wed Mar 23 21:04:18 2016 -0700
./configure --with-dri-drivers= --enable-vdpau --enable-gbm --with-egl-platforms=x11,drm --enable-glx-tls --enable-egl --with-egl-platforms=x11,drm --enable-shared-glapi --enable-texture-float




drm commit 49041c3613dde0b11bf6096b3da498915303abed

xf86-video-ati e592f32f8b5f5873fcc18b10a69dd5e4ccf11073

ignore my previous 2 posts, I forgot

 --enable-glamor with my xserver rebuild

the patch fixes the red colour problem, thank you.