1. Go to theme -> Edit code -> Snippets -> product-variant-picker.liquid
2. Find below code:
<fieldset class="js product-form__input product-form__input--pill">
<legend class="form__label">{{ option.name }}</legend>
{% render 'product-variant-options',
product: product,
option: option,
block: block,
picker_type: picker_type
%}
</fieldset>
3. Replace above code with below code:
{%- liquid
assign optionNames = settings.optionName | split:","
assign useColor = false
for optionColor in optionNames
if optionColor == option.name
assign useColor = true
break
endif
endfor
-%}
{% if useColor %}
<fieldset class="js product-form__input product-form__input--pill">
<legend class="form__label">{{ option.name }}</legend>
{% render 'product-variant-options',
product: product,
option: option,
block: block,
picker_type: picker_type
%}
</fieldset>
{% else %}
<div class="product-form__input product-form__input--dropdown">
<label class="form__label" for="Option-{{ section.id }}-{{ forloop.index0 }}">
{{ option.name }}
</label>
<div class="select">
<select
id="Option-{{ section.id }}-{{ forloop.index0 }}"
class="select__select"
name="options[{{ option.name | escape }}]"
form="{{ product_form_id }}"
>
{% render 'product-variant-options',
product: product,
option: option,
block: block,
picker_type: "swatch_dropdown"
%}
</select>
{% render 'icon-caret' %}
</div>
</div>
{% endif %}