$(".alpha").animate({"background-color":"#09f"}, 3000);
.alpha{
width: 100px;
height: 100px;
background-color: red;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script><script>/*[email protected]://github.com/jquery/jquery-color|jquery.org/license*/(function(a,b){functionm(a,b,c){vard=h[b.type]||{};returna==null?c||!b.def?null:b.def:(a=d.floor?~~a:parseFloat(a),isNaN(a)?b.def:d.mod?(a+d.mod)%d.mod:0>a?0:d.max<a?d.max:a)}functionn(b){varc=f(),d=c._rgba=[];returnb=b.toLowerCase(),l(e,function(a,e){varf,h=e.re.exec(b),i=h&&e.parse(h),j=e.space||"rgba";if(i)return f=c[j](i),c[g[j].cache]=f[g[j].cache],d=c._rgba=f._rgba,!1}),d.length?(d.join()==="0,0,0,0"&&a.extend(d,k.transparent),c):k[b]}function o(a,b,c){return c=(c+1)%1,c*6<1?a+(b-a)*c*6:c*2<1?b:c*3<2?a+(b-a)*(2/3-c)*6:a}var c="backgroundColor borderBottomColor borderLeftColor borderRightColor borderTopColor color columnRuleColor outlineColor textDecorationColor textEmphasisColor",d=/^([\-+])=\s*(\d+\.?\d*)/,e=[{re:/rgba?\(\s*(\d{1,3})\s*,\s*(\d{1,3})\s*,\s*(\d{1,3})\s*(?:,\s*(\d?(?:\.\d+)?)\s*)?\)/,parse:function(a){return[a[1],a[2],a[3],a[4]]}},{re:/rgba?\(\s*(\d+(?:\.\d+)?)\%\s*,\s*(\d+(?:\.\d+)?)\%\s*,\s*(\d+(?:\.\d+)?)\%\s*(?:,\s*(\d?(?:\.\d+)?)\s*)?\)/,parse:function(a){return[a[1]*2.55,a[2]*2.55,a[3]*2.55,a[4]]}},{re:/#([a-f0-9]{2})([a-f0-9]{2})([a-f0-9]{2})/,parse:function(a){return[parseInt(a[1],16),parseInt(a[2],16),parseInt(a[3],16)]}},{re:/#([a-f0-9])([a-f0-9])([a-f0-9])/,parse:function(a){return[parseInt(a[1]+a[1],16),parseInt(a[2]+a[2],16),parseInt(a[3]+a[3],16)]}},{re:/hsla?\(\s*(\d+(?:\.\d+)?)\s*,\s*(\d+(?:\.\d+)?)\%\s*,\s*(\d+(?:\.\d+)?)\%\s*(?:,\s*(\d?(?:\.\d+)?)\s*)?\)/,space:"hsla",parse:function(a){return[a[1],a[2]/100,a[3]/100,a[4]]}}],f=a.Color=function(b,c,d,e){return new a.Color.fn.parse(b,c,d,e)},g={rgba:{props:{red:{idx:0,type:"byte"},green:{idx:1,type:"byte"},blue:{idx:2,type:"byte"}}},hsla:{props:{hue:{idx:0,type:"degrees"},saturation:{idx:1,type:"percent"},lightness:{idx:2,type:"percent"}}}},h={"byte":{floor:!0,max:255},percent:{max:1},degrees:{mod:360,floor:!0}},i=f.support={},j=a("<p>")[0],k,l=a.each;j.style.cssText="background-color:rgba(1,1,1,.5)",i.rgba=j.style.backgroundColor.indexOf("rgba")>-1,l(g,function(a,b){b.cache="_"+a,b.props.alpha={idx:3,type:"percent",def:1}}),f.fn=a.extend(f.prototype,{parse:function(c,d,e,h){if(c===b)return this._rgba=[null,null,null,null],this;if(c.jquery||c.nodeType)c=a(c).css(d),d=b;var i=this,j=a.type(c),o=this._rgba=[];d!==b&&(c=[c,d,e,h],j="array");if(j==="string")return this.parse(n(c)||k._default);if(j==="array")return l(g.rgba.props,function(a,b){o[b.idx]=m(c[b.idx],b)}),this;if(j==="object")return c instanceof f?l(g,function(a,b){c[b.cache]&&(i[b.cache]=c[b.cache].slice())}):l(g,function(b,d){var e=d.cache;l(d.props,function(a,b){if(!i[e]&&d.to){if(a==="alpha"||c[a]==null)return;i[e]=d.to(i._rgba)}i[e][b.idx]=m(c[a],b,!0)}),i[e]&&a.inArray(null,i[e].slice(0,3))<0&&(i[e][3]=1,d.from&&(i._rgba=d.from(i[e])))}),this},is:function(a){var b=f(a),c=!0,d=this;return l(g,function(a,e){var f,g=b[e.cache];return g&&(f=d[e.cache]||e.to&&e.to(d._rgba)||[],l(e.props,function(a,b){if(g[b.idx]!=null)return c=g[b.idx]===f[b.idx],c})),c}),c},_space:function(){var a=[],b=this;return l(g,function(c,d){b[d.cache]&&a.push(c)}),a.pop()},transition:function(a,b){var c=f(a),d=c._space(),e=g[d],i=this.alpha()===0?f("transparent"):this,j=i[e.cache]||e.to(i._rgba),k=j.slice();return c=c[e.cache],l(e.props,function(a,d){var e=d.idx,f=j[e],g=c[e],i=h[d.type]||{};if(g===null)return;f===null?k[e]=g:(i.mod&&(g-f>i.mod/2?f+=i.mod:f-g>i.mod/2&&(f-=i.mod)),k[e]=m((g-f)*b+f,d))}),this[d](k)},blend:function(b){if(this._rgba[3]===1)return this;var c=this._rgba.slice(),d=c.pop(),e=f(b)._rgba;return f(a.map(c,function(a,b){return(1-d)*e[b]+d*a}))},toRgbaString:function(){var b="rgba(",c=a.map(this._rgba,function(a,b){return a==null?b>2?1:0:a});return c[3]===1&&(c.pop(),b="rgb("),b+c.join()+")"},toHslaString:function(){var b="hsla(",c=a.map(this.hsla(),function(a,b){return a==null&&(a=b>2?1:0),b&&b<3&&(a=Math.round(a*100)+"%"),a});return c[3]===1&&(c.pop(),b="hsl("),b+c.join()+")"},toHexString:function(b){var c=this._rgba.slice(),d=c.pop();return b&&c.push(~~(d*255)),"#"+a.map(c,function(a){return a=(a||0).toString(16),a.length===1?"0"+a:a}).join("")},toString:function(){return this._rgba[3]===0?"transparent":this.toRgbaString()}}),f.fn.parse.prototype=f.fn,g.hsla.to=function(a){if(a[0]==null||a[1]==null||a[2]==null)return[null,null,null,a[3]];var b=a[0]/255,c=a[1]/255,d=a[2]/255,e=a[3],f=Math.max(b,c,d),g=Math.min(b,c,d),h=f-g,i=f+g,j=i*.5,k,l;return g===f?k=0:b===f?k=60*(c-d)/h+360:c===f?k=60*(d-b)/h+120:k=60*(b-c)/h+240,h===0?l=0:j<=.5?l=h/i:l=h/(2-i),[Math.round(k)%360,l,j,e==null?1:e]},g.hsla.from=function(a){if(a[0]==null||a[1]==null||a[2]==null)return[null,null,null,a[3]];var b=a[0]/360,c=a[1],d=a[2],e=a[3],f=d<=.5?d*(1+c):d+c-d*c,g=2*d-f;return[Math.round(o(g,f,b+1/3)*255),Math.round(o(g,f,b)*255),Math.round(o(g,f,b-1/3)*255),e]},l(g,function(c,e){var g=e.props,h=e.cache,i=e.to,j=e.from;f.fn[c]=function(c){i&&!this[h]&&(this[h]=i(this._rgba));if(c===b)return this[h].slice();var d,e=a.type(c),k=e==="array"||e==="object"?c:arguments,n=this[h].slice();return l(g,function(a,b){var c=k[e==="object"?a:b.idx];c==null&&(c=n[b.idx]),n[b.idx]=m(c,b)}),j?(d=f(j(n)),d[h]=n,d):f(n)},l(g,function(b,e){if(f.fn[b])return;f.fn[b]=function(f){var g=a.type(f),h=b==="alpha"?this._hsla?"hsla":"rgba":c,i=this[h](),j=i[e.idx],k;return g==="undefined"?j:(g==="function"&&(f=f.call(this,j),g=a.type(f)),f==null&&e.empty?this:(g==="string"&&(k=d.exec(f),k&&(f=j+parseFloat(k[2])*(k[1]==="+"?1:-1))),i[e.idx]=f,this[h](i)))}})}),f.hook=function(b){var c=b.split(" ");l(c,function(b,c){a.cssHooks[c]={set:function(b,d){var e,g,h="";if(d!=="transparent"&&(a.type(d)!=="string"||(e=n(d)))){d=f(e||d);if(!i.rgba&&d._rgba[3]!==1){g=c==="backgroundColor"?b.parentNode:b;while((h===""||h==="transparent")&&g&&g.style)try{h=a.css(g,"backgroundColor"),g=g.parentNode}catch(j){}d=d.blend(h&&h!=="transparent"?h:"_default")}d=d.toRgbaString()}try{b.style[c]=d}catch(j){}}},a.fx.step[c]=function(b){b.colorInit||(b.start=f(b.elem,c),b.end=f(b.end),b.colorInit=!0),a.cssHooks[c].set(b.elem,b.start.transition(b.end,b.pos))}})},f.hook(c),a.cssHooks.borderColor={expand:function(a){var b={};return l(["Top","Right","Bottom","Left"],function(c,d){b["border"+d+"Color"]=a}),b}},k=a.Color.names={aqua:"#00ffff",black:"#000000",blue:"#0000ff",fuchsia:"#ff00ff",gray:"#808080",green:"#008000",lime:"#00ff00",maroon:"#800000",navy:"#000080",olive:"#808000",purple:"#800080",red:"#ff0000",silver:"#c0c0c0",teal:"#008080",white:"#ffffff",yellow:"#ffff00",transparent:[null,null,null,0],_default:"#ffffff"}})(jQuery);
</script>
<div class="alpha"></div>