On the light pink background, I suggest that deep purple is more conspicuous and can be used to write the main title. Deep purple and light pink are warm colors, and the brightness is quite different, but it is not very abrupt.

The composition suggestion of the new poster is to highlight the title, which can be supplemented by cartoon characters or flowers. The lower right corner belongs to the name of the school organization. ?

The following is the welcome poster I made before, hoping to give you a reference.