wffweb/src/main/java/com/webfirmframework/wffweb/css/RgbaCssValue.java
public void setA(final float a) {
        if (a < 0 || a > 1) {
            throw new InvalidValueException(
                    "a paramater accept values only from 0 to 255.");
        }
        this.a = a;
        rgba = "rgba(" + r + ", " + g + ", " + b + ", " + a + ")";
        if (getStateChangeInformer() != null) {
            getStateChangeInformer().stateChanged(this);
        }
    }
public void setA(final float a) {
        if (a < 0 || a > 1) {
            throw new InvalidValueException(
                    "a paramater accept values only from 0 to 255.");
        }
        this.a = a;
        rgba = "rgba(" + r + ", " + g + ", " + b + ", " + a + ")";
        if (getStateChangeInformer() != null) {
            getStateChangeInformer().stateChanged(this);
        }
    }
to set alpha. The default value is 0.

@param a
@author WFF
@since 1.0.0