could not convert string to float: 'YELLOW'

import numpy as np
import pandas as pd
from sklearn.neural_network import MLPClassifier
from sklearn.metrics import accuracy_score
from sklearn.model_selection import train_test_split
from sklearn.metrics import confusion_matrix

#read data
data=pd.read_csv('adult-stretch.data', header=None)

#convert to arrays
x=data.iloc[:, :4].to_numpy()
t=data[4].replace(['ADULT','STRETCH'],[0,1])

t=t.to_numpy()

#split the dataset
xTrain, xTest, tTrain, tTest = train_test_split(x, t, test_size=0.2, random_state=3)
#split - 

#create the model/net
net=MLPClassifier(hidden_layer_sizes=(2,), max_iter=4000, random_state=0) 

 #model training
net=net.fit(xTrain,tTrain)   

#model run/testing for TRAIN
yTrain=net.predict(xTrain)    

accuracyTrain=accuracy_score(tTrain,yTrain)    #accuracy!!
print('Train accuracy is ',accuracyTrain)

#model run/testing for TEST
yTest=net.predict(xTest)    

accuracyTest=accuracy_score(tTest,yTest)    #accuracy for test
print('Train accuracy is ',accuracyTest)

M=confusion_matrix(tTest,yTest)
print(Confusion matrix= ) 
print (M)