(I'm not a geologist, just helping my kids collect rocks).
It is confusing - both rocks are commonly pink overall. But, granite has abundant quartz, syenite has no quartz to very little. Quartz will be the grey translucent mineral that looks just like a blob with no distinct shape.
You can use this website: https://www.virtualmicroscope.org to see examples of syenite and granite (use the search box).