Вы можете использовать rgba (255,0255,1)
<svg class="svg_element" style="margin-top:0px;margin-left:560px">
<circle cx="25" cy="25" r="20" fill="rgba(128, 0, 128, 0.75)"
stroke="rgba(0, 255, 0, 0.25)" stroke-width="10"/>
<circle cx="75" cy="25" r="20"
fill="rgba(0, 255, 0, 1)"
stroke="rgba(0, 0, 255, 0.1)" stroke-width="10"/>
<circle cx="125" cy="25" r="20"
fill="rgba(255, 255, 0, 0.75)"
stroke="rgba(255, 0, 0, 0.25)" stroke-width="10"/>
</svg>
здесь скрипка