By default, YouTube offers 9 color schemes to colorize its video player for embedding. Although color customization of YouTube player is very flexible, since it can be manipulated using hex color codes, YouTube is not providing any easy way to do so for whatever reason.
There is no way else to get more creative with colors, unless you edit the hex color code in the embed code, or use a third party tool.
Using VTubeTools to customize YouTube player color
VTubeTools is a YouTube video customizer, providing options like autoplay, flexible resizing, coloring, border, allow/disallow full screen, loop, display related videos, high quality and custom player background.
Since a color palette is included, it makes life much easier. After selecting colors from the color palette, you can have a preview first before grabbing the new embed code.
A sample video player color that is not included in the default 9 color schemes offered by YouTube:
I made it autoplay, for the lulz
Do it manually, edit the hex color code in the embedding code
If the tool above is not working, you can opt to do it manually, by editing the hex color codes (highlighted in red below) in the embedding code. Just simply modify them to the color you desire. Use this hex code generator if you have no idea what hex codes are.
<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/oHg5SJYRHA0&hl=en&fs=1&color1=0x3a3a3a&color2=0x999999"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/oHg5SJYRHA0&hl=en&fs=1&color1=0x3a3a3a&color2=0x999999" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>
Make sure the # symbol is not included.