i cant chose my own color in recolor

The colors you see in the Recolor gallery are determined by the current theme colors, as set on the Design tab. The selections include the "Background" color and the six "Accent" colors. These colors are also used for font colors in some headings and for some other features.

You can choose a different theme by clicking the Themes button on the Design tab and selecting from the gallery. Alternatively, you can modify the set of colors used by any theme (built-in or custom). On the Design tab, click the Colors button and select one of the color sets (such as the one named Violet). Or click the Customize Colors item at the bottom of the gallery, which opens a dialog where you can change any or all of the colors of the current selection.

Or you can did down in the menu ...

With the image selected, the Picture Tools > Format contextual tab is displayed.  Go to Adjust group > Color drop down > More Variations command > More Colors command > Custom tab. Here you can select an color visually, or set using explicit RGB or HSL values.

Note that the Format Picture Pane does not offer the option of making that sort of color change.

And because the background was a consistent color you can hide it by using the Adjust group > Color drop down > Set Transparent Color command to get this:

Note: I did a right click, save picture from Word. I was surprised to see that recoloring was not exported. I just got the original image.  I had to do a screen capture to be able to show the above change.